Very long title, but I was unsure of how to name the thread lmao
I've been doing a few playthroughs now. The first time I recruited all of the companions, other times I only recruited one or two and switched it up in other playthroughs to see if anything would play out differently.
Something I noticed is that alternate scenes sometimes play when you don't have all the companions in your party. The most prominent examples of this (that I've found, at least) are if you don't recruit Lae'zel and Shadowheart, but have Astarion in the party.
Provided you've used the tadpole enough times, but haven't recruited Lae'zel, the night where
you all feel sick and she comes at you with a knife
doesn't happen, but instead you get a longer conversation with Astarion, who otherwise just tells you to go away. It's not exactly an alternate scene; he doesn't replace Lae'zel in what she tries to do, but it merely makes for a bit of a longer dialogue with a persuasion check, which allows you to get to know him just a litte bit better.
Usually I think it's really neat with alternate scenes based on which companions you've got with you; it's a lot more work, but it can definitely pay off. In this particular case, I personally think it'd be nicer to keep the longer dialogue, since the scenario remains the same regardless if Lae'zel is there or not, just without her initial scene.
There was a similar scene taking place if you don't recruit Shadowheart, with
Astarion having a nightmare.
I think it makes more sense for this scene to only happen if you don't have SH in your party (since there's a scene with her playing out otherwise), but it's still a bit of a shame to have to choose between it and having a specific party member with you. Especially since the alternate scene also shows a bit of a conversation occurring between party members, which doesn't happen too often aside from the occasional banter while walking around.
There might be more examples like these in the game featuring other companions, but so far I haven't found many. I hope what I wrote made sense; English isn't my first language, so sorry for any confusing sentences!