Unlike every single Mainstream Pokemon Game outside of Pokemon Yellow, players actually won't have the option of selecting their Starter Pokemon in Pokemon: Let's Go, Pikachu. Instead, players will be locked into having Pikachu, the game's namesake, as their Starter Pokemon. This same thing was found in Pokemon Yellow over two decades ago, the same where players could only have Pikachu (as well) as their Starter Pokemon.
Unlike other Starter Pokemon from previous Mainstream Titles, this Pikachu will be special in a number of ways. In addition to traveling outside of its Poke Ball, players can personally dress Pikachu in a number of outfits and accessories and take care of it like they would any Pet in the real world (grooming, Petting, Feeding, etc.). Unlike other Pikachu, the one you will receive as your Starter Pokemon in Pokemon: Let's Go, Pikachu also won't be able to evolve.