Not sure, the only game I played before BG3 was Dark Alliance 2 on PS2 around 20 years ago. Well that and homebrew 3.5e/5e tabletop, but that obviously was unrelated story-wise.

Yeah, not sure who was in which games, but Minsc and Jaheira were grouped with one of the protagonists, and at least one of the games had another Bhal spawn.

Somewhat. It’s story is mostly independent, but it does take place after 2 and therefore has canonized several of the decisions you could make in 2, as well as a few returning characters.