Somehow it seems like I am the first person to make a post about this new meta. Neat. I have been following the different LGPE metagames for a while, but I am no expert. Despite playing some games where onlookers might speculate that I was trying to lose, I managed to get to the semifinals in the inaugural Cup for LGPE UU. A disclaimer here is that this metagame is extremely young, and I am far from the most seasoned player of the metagame, or LGPE at large, so fully anticipate these takeaways being utterly trashed in due time. Anyhow, I've sorted my opinions in little categories to make your reading experience as digestible as possible.
Metagame Centralization (And Pokemon That I Think Are Bad)
This metagame is pretty centralized. It's not quite an RBY LT where you can choose from a pool of about nine Pokemon and get away with it at least most of the time, but I would be hard pressed to name more than like maybe two dozen Pokemon that are actually worth using. With a small pool of Pokemon and no abilities, items, EV spreads, etc., there just aren't a ton of emergent strategies and tactics (which is not an insult by the way... I'm an RBY main). As a result, there isn't really a ton of room to "get one over" a competent and knowledgeable player. I expect teams and games to homogenize over time, with balanced/bulky offensive builds being the norm. Pivoting and positioning will be the major decider of games. Anyhow, here are some Pokemon that are presently ranked in LGPE UU that are way over-ranked or should probably be in RU. The order is based on the current VR.
Lapras
Despite this Pokemon being the literal #1 Pokemon on the old UU VR, I never considered it for a team for even a second. It is very slow, weak to Stealth Rock, and offers very little in the way of status moves. Water-type Pokemon, while good, are a huge liability in a metagame where Electrode is the best win condition. Ice Shard is kind of its only appealing trait, and I guess it handles Shell Smash users well. Snorlax is a much more reliable trade bot if that's what you want on your team.
Chansey
Basically nobody touched this thing for the entire tournament. It seems decent for endgames because a lot of the best late game Pokemon are specially-oriented (Electrode, Mega Pidgeot, Alolan Nineteales, etc.), but I think it is probably too much of a gamble in the builder and it has a pretty small midgame presence. I thought about building with it a few times and maybe it could be good, but I think the meta is too fast and aggressive for it.
Starter Pikachu
Starter Pikachu has a lot of really nice traits: high speed, good coverage, priority, and a solid typing. However, its damage output is pitiful and basically every move in the game can 2HKO it or better. I think Electrode is honestly just better and running both is really not necessary. Electrode cleanly 2HKOing this with Foul Play is never not funny.
Alolan Persian
This is another Pokemon I thought about building with a few times. U-turn and STAB Foul Play are actually really nice traits. But that's kind of it. Outside of Speed, its stats are just awful. This isn't providing much offensive pressure and everything will KO it easily.
Starter Eevee
Same story as Starter Pikachu. Great utility options, but it has no offensive presence and seemingly everything can 2HKO it or better. Sparkly Swirl on Rest-centric teams is an idea, but this Pokemon is a complete momentum sink to get in and actually use as a cleric. You are pulling off Sparkly Swirl one time in a game, at best.
Alolan Sandslash
This walls Alolan Ninetales but honestly I have no idea what else it does. Stealth Rock has other users and Fighting- and Ground-type coverage are everywhere to destroy this.
Dugtrio
I like this in theory on HO teams where you literally just need Stealth Rock around turn 1 and nothing else, but I don't know how viable that style actually is. It might have some sweeping potential. It has low staying power and ultimately pretty limited utility.
Vileplume
I genuinely have no idea why you would use this over Exeggutor or Victreebel. It's also atrociously slow.
Tentacruel
This one might be alright, but the damage output is just low, and a lot of really solid Pokemon give it trouble, like Snorlax and Electrode.
And here are a few that are on thin ice, or I am unsure about.
Wigglytuff
This barely saw any use, but it might be alright. I don't think its role compression is actually that useful, especially when compared to other Stealth Rock users, but it does have some nice tools and a decent defensive typing. Maybe something is there, not sure.
Arcanine
Arcanine is actually totally fine, but I'm putting it here because I honestly don't know if it's the best Fire-type Pokemon. I think Alolan Ninetales keeps Fire-type Pokemon in business, so one of them ought to be good, but I genuinely haven't done my homework to prove which one is actually the best. It very well could be Aracnine though. Rapidash seems okay on paper.
Moltres
This thing is really awkward to build with and is ruined by Stealth Rock. It has some nice tools though and an actual damage output.
Kabutops
I don't really think thing has much of a niche. The typing is honestly not great. Versus most other Stealth Rock users, it gets a resistance to Flying- and Normal-type moves, but awful weaknesses to Electric-, Ground-, Grass-, and Fighting-type moves. Unlike most other Stealth Rock users, it isn't a pocket Electrode check in the slightest, so teams with Kabutops often need to start stacking weaknesses to actually handle Electrode.
Omastar & Cloyster
Shell Smash is cute, but Electrode is everywhere. They feel so bad to use and probably don't belong in UU, but on paper they feel like they should at least be decent. Omastar, perhaps unexpectedly, seems to be the better of the two. I do wonder if Cloyster has any value as a dedicated defensive Pokemon, but a lack of notable resistances really hurts. Fun fact: Ice/Water, along with Ice/Psychic, is the only type combination that resist no types but the types in the combination itself.
Mega Pokemon
The Mega Pokemon in this metagame are not created equal. I don't think having a Mega Pokemon is actually strictly necessary, as I think several are actually pretty bad, and even the good ones come with major shortcomings against key Pokemon. You can probably slap Mega Pidgeot or Mega Slowbro on more teams than you can't, but I don't think you ever technically need to.
Mega Kangaskhan
This thing is actually so underwhelming. STAB Fake Out is genuinely it's only good trait that's at all unique. You give up the ability to Mega Evolve a much better Pokemon to gain access to what: 125 Attack and 100 Speed? Sad. Mega Kangaskhan also suffers from having no moves with any kind of Base Power behind them, while also being liable to find itself short on the correct coverage option. It has some use because it's actually a physical attacker, but I think Slowbro or Pidgeot is still a better choice and Pokemon like Snorlax and Tauros can usually do its job fairly well without eating the Mega slot. I actually only used Mega Kangaskhan when I already had Tauros and Snorlax on board, in an attempt to get a Normal Spam team going.
Mega Pidgeot
Hey look, a good Pokemon! Mega Pidgeot is pretty one-dimensional in terms of sets, but it can afford to be when that set has healing and pivoting on top of real stats. Mega Pidgeot offers an offensive output at 135 Special Attack and 121 Speed, superior to pretty much every other Mega Evolution. It does admittedly have some issues with revenge killing, as it invites in Electrode all day, and its limited coverage can make some Pokemon fairly difficult to damage, though U-turn helps a little with the latter issue. I also tried Hyper Beam on this once. Never clicked it, but check the calcs. On a good predict, it can wipe out a bunch of troublesome Electric-type Pokemon, among others. Also, screw Air Slash.
Mega Slowbro
I think Mega Slowbro is good but I'm honestly not sure what this thing is actually best at. Towards the end of the tournament, I began favoring three- and four-attack builds, but things like Calm Mind, Thunder Wave, Rest, and Screens seem to have merit. It always felt at least fairly solid though. Stuffing out physical attackers is really nice for some teams, but Thunderbolt and Mega Drain do just obscene amounts of damage to it, so it requires some positioning, especially on late-game set up builds.
Mega Pinsir
This thing is pretty awful. If Pinsir wasn't very good on its own merits, I don't think this belongs in UU. The Attack stat is great, but that's about it. The Speed tier is awkward, the Stealth Rock weakness (and without healing) is miserable, and the coverage is insufficient. This Pokemon kind of has to lead, but it really interferes with your Stealth Rock game if you do this. Electrode eats this thing alive and other common endgame Pokemon like Alolan Ninetales, Mega Pidgeot, Tauros, and Dodrio can easily dispatch it. Rock-type coverage is actually pretty good already, so you can pretty easily tech for this thing if you're ever worried about it.
Mega Charizard Y
This is basically just special-attacking Mega Pinisr, but the Speed tier and base form are worse. Like Pinsir, it probably has some merit on more aggressive builds that can somehow get by without setting Stealth Rock early, but I think that's more of a matchup or skill check than anything. Water-types are actually not extremely dominant in this tier though, so that's kind of nice.
Other Pokemon
Here are some notes that I felt like sharing about specific Pokemon and archetypes.
Snorlax
Snorlax is the best Pokemon in the tier. It's extremely difficult to exploit, it can pocket check pretty much every dangerous sweeper because it's basically impossible to OHKO even after Stealth Rock, and it has an amazing array of moves to use. It's probably the only Pokemon that belongs on like every team.
Electrode
Electrode is also really good. Thunderbolt and Foul Play are basically all this needs to function. I'm actually amazed by how good of a click Foul Play is in this meta. Pretty much everything is 4HKOed or better by it, which doesn't sound crazy, but it does basically mean most Pokemon only get one or two switches into it. Reflect, Light Screen, Thunder Wave, and Explosion are all nice utility options to play with. I ran this Pokemon on pretty much every team. Good players can exploit it with powerful Pokemon like Nidoking and Sandslash, but it's still really good. I'd recommend making room for it on most teams and always preparing a thorough plan for dealing with it. It's extremely centralizing.
Stealth Rock
Nothing ground-breaking, but Stealth Rock is extremely good here. It helps secure a lot of knock outs, impedes defensive play immensely (most healing in this meta is from Roost on Flying-type Pokemon), and turns revenge kill attempts into checkmates. Get them up early. I often strove for turn 1 Stealth Rock, but that is pretty predictable and can be punished with good play. But regardless, try to get them up quickly. Basically every decent or better win condition (Electrode, Kingler, Dragonite, Alolan Ninetales, Mega Pidgeot, etc.) loves support from Stealth Rock and hates seeing them on their side. Do not drop Stealth Rock.
Thankfully, most of the Stealth Rock users actually offer a lot of utility, so you get variety to pick from when crafting your team. Nidoking has great coverage, can go physical, special, or mixed, and can slow down Electric-type Pokemon. I never really figured out its best set(s). Sandslash can also slow down Electric-type Pokemon and has a surprisingly good damage output on top of a decent boosting option if it wants. Pinsir has a solid Speed tier (same as Nidoking), pretty unique and strong coverage, and a typing that a lot of opposing Stealth Rock users and anti-leads can't exploit too easily. Wigglytuff, Kabutops, Dugtrio, and others also have some fun tools to offer.
Golem
I like Golem. A terrible Speed and mostly poor defensive typing make it a tough Pokemon to include on a team and somewhat difficult to pilot. However, it does handle three of the best Pokemon in the metagame, Snorlax, Electrode, and Mega Pidgeot, pretty well. It can be a Stealth Rock user, but I don't know if it has to be one. I wanted to use Golem a lot more, but just never really got around to building with it. I think its damage output and overall utility make it a firm member of UU.
Sleep-inducers
Sleep is kind of broken and should probably be banned for LGPE at large. This metagame is way too offensive to handle losing a Pokemon entirely for potentially several turns because a low-accuracy move happened to hit.
Alolan Ninetales I think is an excellent and underrated Pokemon. It boasts strong coverage and a great Speed stat. It also has a great natural synergy with solid Pokemon like Electrode and Mega Slowbro. I think the sweeping offensive core of Alolan Ninetales and Electrode is one of the best in the game. It's also a decent lead thanks to an incredibly fast Sleep and a good hit on most Stealth Rock users. It can be countered in the builder though with intentional prep, and Snorlax can bully it if played well.
Exeggutor and Victreebel are both solid. I find Exeggutor better because it seems sturdier and I think the typing is better, especially as you take Earthquake much more comfortably. Victreebel does make up for its shortcoming though with a slightly better Speed, mixed options, Swords Dance, and Sucker Punch.
I never really had any interest in Poliwrath. It's very weak to a lot of very good Pokemon, like Electrode, Mega Pidgeot, Mega Slowbro, and Alolan Ninetales. It is pretty solid into some important Pokemon though, like Snorlax and most Stealth Rock users. Hypnosis gives it another solid tool.
I also thought a bit about Jynx because it has a pretty good Speed tier and Lovely Kiss is relatively accurate. It honestly might be decent, but it sure is frail.
Agility-users
I'm not a huge fan of Dragonite because I think its Stealth Rock weakness and reliance on Outrage make it an inconsistent sweeper. I think it actually has more merit as an early game breaker using its wide array of mixed attacks. Thunder Wave is a nice option too. It's ultimately alright. I think Kingler is a bit more consistent at actually getting a sweep done. While a lot of Pokemon just obliterate it, it does have some good set up opportunities and basically all the coverage it needs. Again, maybe a little inconsistent, but good and something to prepare for. Agility users are also some of the few actual win conditions in this tier.

The Remaining Pokemon That Are Somewhat Interesting
I didn't mean to go through like every Pokemon in the tier, but I got really close to covering all them so I figured I might as well close out with those that I missed.
Tauros honestly isn't great at anything in particular, but it's a pretty low cost Pokemon to add to a team thanks to a high Speed, acceptable bulk, and only one weakness. I don't usually feel like a team needs it, but it doesn't usually feel bad to add it. I usually ran Double-Edge, Earthquake, Rock Slide, and Facade because I didn't really know what else to do with those last two slots.
Dodrio is pretty similar to Tauros, having better damage output but much worse defensive potential. Being now at 110 Speed now is very nice.
Primeape isn't really great, and I felt it was pretty underwhelming. It is the only Fighting-type with a real Speed stat though, which is good for role compression, and U-turn can be nasty.
Slowbro is honestly pretty mediocre with a handful of relevant weaknesses, but it can function as a physically defensive pivot and it kind of works on teams looking to try out two possible Mega Pokemon (usually it and Pinsir, realistically) at the same time.
Electabuzz is alright, but I don't think having two Electric-type Pokemon is ever super necessary and Electrode will normally be better. Speed is king.
Win Conditions & Team Archetypes
For this section, I'm going to drop some ideas on routes to victory in a game, and how I evaluate them. This is kind of a mix of Pokemon, strategies, and team styles. Like most of this post, nothing is set in stone here. It's simply some musings on how I view progress making and securing endgames at this point in the metagame.
Electrode Offense
When I first looked at LGPE UU, my eyes immediately went to Electrode. Coming primarily from RBY, especially its low tiers, the fastest Pokemon with an even acceptable damage output is very often a great starting point. In tiers with no items and abilities for boosting Speed as well as relatively few moves to do it (and even those that can use Speed-boosting moves are sometimes still slower), the fastest Pokemon provides an unparalleled value in endgames because they are uniquely capable of stringing together multiple knock outs in succession. When I saw it learned Foul Play, I was sold. Most of my teams were built around Electrode winning the game. The general idea is to just get Stealth Rock up, maybe put something to sleep, and neutralize the opponent's Ground-type. Longer games favor you because you get more Stealth Rock chip for the sweep (while Electrode itself doesn't really care too much because it only needs to come in a few times and likely won't be getting hit too many times along the way). Solid bulky Pokemon like Snorlax, Sandslash, and Exeggutor are natural partners. Alolan Ninetales, as said above, is a cheeky secondary sweeper option that can eliminate Electrode's checks, or even sweep itself instead if your opponent invests too many resources in checking Electrode.
Boost Sweeping
Rather than relying on Electrode's natural Speed, these teams look to chain knock outs with something that can boost Speed first. Dragonite, Kingler, and Shell Smash users are your main options here. The benefit to these sweepers is that they have broader coverage and higher damage output than Electrode. However, taking a turn to set up, and often being slower than Electrode anyway, make the teams they're on a bit shakier overall. You also might need to get Reflect or Light Screen to last just the right number of turns. I found the positioning requirements to get these teams going a bit daunting so I seldom tried them. That said, they are probably functional with good piloting. Sweepers that aren't Electrode aren't as innately covered in the builder because they are less expected and more varied in coverage.
Swords Dance and Nasty Plot sweepers can kind of work, but none of them are really fast enough to actually sweep on their own. Mega Pinsir and Alolan Ninetales get the closest, but they can still be stuffed by Pokemon like Tauros, Mega Pigeot, and, of course, Electrode. Victreebel can also become a Pseudo Extreme Killer with Sucker Punch, Swords Dance, and Substitute, but this has obvious inconsistencies.
Mega Slowbro can also be a good win condition with Calm Mind and Rest. This requires a lot of set up and a lot of things can easily go wrong along the way, but a heavily boosted Slowbro can be very difficult to handle for a lot of teams.
Stacking multiple Shell Smash sweepers to make an HO build was also something I thought about. Maybe that works.
Substitute is also pretty nice to get free turns, especially in tandem with Sleep or Paralysis. Paralysis is a bit tricky to use, especially with Electric- and Ground-type Pokemon being common, but I think it can be rather dangerous if exploited well.
U-turn & Teleport Spam
Building a team centered around pivoting was something I tried, but it never fully came to fruition. In theory, I think supporting a heavy hitter, like Snorlax or Dodrio, or a dangerous boost sweeper, like Kingler, Sandslash, or Mega Pinsir, with one or more pivoting Pokemon could potentially be very dangerous. It has some issues in practice though. U-turn doesn't have a ton of great users, and using the best one, Mega Pidgeot, keeps you from getting a high damage output from a different Mega Pokemon. Most U-turn users are also rather fast, so getting a safe switch into a frail heavy hitter is actually pretty rare. A lot of them like Persian, Alolan Persian, and Fearow are also just not the best, though I did seriously consider each of these Pokemon at least once. Teleport gets around this to some extent, but without things like Leftovers and Regenerator, using Teleport more than once or twice is pretty hard. While Teleport users are generally bulky, they tend to have pretty exploitable weaknesses, so you have to pivot them in first before you can even pivot them out, which is kind of counterproductive. Perhaps ignoring the "bring in a big attacker" part might be an idea, as the U-turn users themselves do have a decent damage output and array of coverage options. They might be able to sustain offensive momentum on their own. Screens also might work here. I would like to see this idea realized one way or another though, because I think there is something here.
Outdamaging Your Opponent
In RBY, and perhaps other communities, we have a simple concept called "outdamaging your opponent." This is when you cast aside any mentality to set up for chain knock outs, boosting, and whatnot and just focusing on hitting the opponent harder and more often than they hit you. Outside of Stealth Rock, the occasional use of Screens, and maybe Sleep-inducing moves, these teams are mainly just looking to click attacks. I think teams composed of just a good number of the tiers hardest hitters like Tauros, Snorlax, and Mega Pidgeot could have merit. There's not too much to say here because this strategy does kind of just resolve to "hit for what will do the most damage most of the time." A lot of teams in this "archetype" look like Electrode builds, but might choose to eschew Electrode and may favor faster Pokemon over bulkier ones.
I'm also going to mention Rest + Sparkly Swirl builds here, because in theory you land more attacks this way (and I have nowhere else to put them). But again, Starter Eevee is so weak and loses so much momentum, on top of the momentum lost by clicking Rest, that I think the strategy is close to unviable.
Stall and Defensive Play
This doesn't work. The only positive thing I have to say here is the move Toxic could maybe be underrated. However, hard stall is just not viable here. Stealth Rock damage mounts up way too quickly, healing is way too sparse, and offensive threats are way too diverse. Most Pokemon deal way too much damage to properly stall long-term, and even if you do stall them, you risk losing to critical hits, status effects, and boost sweepers.
Natures
I'm not really one to delve into the weeds of EV spreads, so even the relatively simplistic world of natures was a little confusing. Outside of Pokemon where Speed really isn't super relevant and some calculations are, like for Snorlax, Sandslash, and Electrode, I defaulted to thinking running max Speed is basically always the best option. Not sure if this is actually the case, but it seemed to work pretty well. Going first is good. It does mean though you probably want to be just a physical or special attacker, so you can minimize the unused attack stat at no cost.
Overall, LGPE UU is a fun metagame. I think there is a ton to learn here and I hope to explore more later on. I also might drop a proper VR. I hope an official one is made soon to restructure RU. I think my VR will have around 20 Pokemon in UU. Also, consider drafting me for LGPL II. Cheers!