Yeah, you can add many profiles to the Switch and each game gets its own save per profile — the only exception to this I know of is Animal Crossing, where each profile has their own character but each Switch has 1 island shared among all profiles

Technically the included controllers are enough for 2 people, but they’re quite small when used individually. I’d suggest a 2nd pair.

The charging port is in the same spot on both the OLED and original. There are probably some 3rd party docks out there that double as a stand which don’t block the screen that might work for charging while playing.

Mario Kart, Smash Bros, Mario 3D World, can’t really go wrong with multiplayer Mario games. The new Zelda (Tears of the Kingdom) is great, but single player — however it can be great fun to watch others play as well so taking turns may be fine