https://www.gamespot.com/articles/lets-go-pikachu-eevee-version-exclusive-pokemon-re/1100-6460367/

The upcoming Pokemon RPGs for Nintendo Switch, Let's Go, Pikachu and Let's Go, Eevee, are set to launch this November, and The Pokemon Company has shared a few new details about the new games. Along with a new trailer, the company revealed that some monsters will only be available in each version.

As in previous Pokemon RPGs, Let's Go, Pikachu and Let's Go, Eevee will each feature a handful of exclusive Pokemon that cannot normally be obtained in the other game. Oddish, Sandshrew, and Growlithe have been confirmed to only appear in Let's Go, Pikachu, while Bellsprout, Vulpix, and Meowth will only be available in Let's Go, Eevee.