I've been comparing BG2 and BG3 almost solely on their stories but that's because it's the most interesting part to me. That said the differences between a 6 and 4 man squad can certainly change the tenor of combat encounters but I think this has more to do with the relative power curves between 2nd and 5th edition than anything
I'd would put Kingmaker much closer to BG:1 than BG:2 and really just the first Act of Baldur's Gate.
