In Pokemon let's go eevee/Pikachu is the starter stronger than just a normal eevee? I wanna say it is but I have no clue.
Partner Eevee has 435 BST compared to Eevee's 325. Partner Pikachu has 430 compared to Pikachu's 320. Both Partner Pokemon are able to learn moves their regular forms cannot; thus, the two are considered stronger than normal.
Pikachu (Pokemon Database) Eevee (Pokemon Database)