I decided to try Will-o-wisp Mew to enable a setup, instead of using Transform once the setup is complete. In testing I found that opponents would target Mew early in the game to try to deny a potential Transform + Mega Tyranitar sweep, so Will-o-wisp was more successful as it crippled potential threats to Tyranitar. Will-o-wisp also protects the team against threats that it would otherwise be quite weak to, such as banded Zygarde and packs a bit of surprise factor into the team. Electrium Z Koko + Kartana give the team 2 good ways of pressuring Tapu Fini, ensuring Misty Terrain stays off the field so Mew can spread burns. Kartana is also nice as a second tailwind setter. Special Lando-T adds intimidate and some extra coverage. Mega Tyranitar was the set up mon and Mega of choice, giving the team a proper psychic resist/immunity as well as a good check against weather teams, Charizard-Y in particular. Finally Volcanion rounds out the team, giving it a water immunity, fire coverage and phasing to prevent trick room or opposing setup.
The gameplan usually revolves around dealing with the opponent's speed control and Tyranitar checks via Mew, Tapu Koko and Kartana, hopefully either securing the speed advantage or putting Tyranitar in position to sweep to close out the game.
Replay:
https://replay.pokemonshowdown.com/gen7doublesou-839845503
Mew crippled Kartana turn 1 and my own Kartana KO'd Suicune to give me speed control at the end of the game, where Kartana and Tyranitar were able to run through my opponent's team in a close finish.
Non-standard set details:
252 SpA Life Orb Tapu Lele Psychic vs. 64 HP / 192 SpD Kartana in Psychic Terrain: 231-273 (84 - 99.2%) -- guaranteed 2HKO
I chose to run adamant Kartana over jolly because of the extra power that adamant provides and to allow Mew to outspeed Kartana and use Super Fang in tailwind before Kartana moves, allowing Kartana to pick up easy beast boosts with a double target. Kartana now speed ties with timid Tapu Lele so I made sure it could live a Psychic in terrain, just in case.
The Lando set is taken from the EV spread compendium, I just moved a few points from Spa to speed make sure it could outspeed AV Kyurem-Black.
Adamant Mega Tyranitar outspeeds modest Tapu Koko at +1. Since Mega Genar's ban many people have started to use modest over timid on Koko. Using adamant over jolly on Mega Tyranitar doesn't actually make much of a difference at +1 speed, aside from the aforementioned timid Koko, Mega Salamence and Naganadel are the only mons on the VR that +1 jolly Tar outspeeds but + 1 adamant does not.
164+ SpA Volcanion Steam Eruption vs. 252 HP / 24 SpD Incineroar: 396-468 (100.5 - 118.7%) -- guaranteed OHKO
112 Speed EVs on Volcanion ensure you outspeed Mega Manectric in tailwind, the rest dumped into hp.