Where can you find Mew/Mewtwo in Pokémon Go?
You can find Mew by completing special research tasks. You can also find Mewtwo by fighting Giovanni or battling it in Raids. You can't 'find' Mew and/or Mewtwo in the wild. Hope that helped!
You can get mew by completing a Mythical Discovery, and Shiny Mew by completing All in one #151 but I think the shiny mew is over :(
Mewtwo is from ex raids and giovanni may use shadow mewtwo. There's also a chance of shiny