I didnt play any D:OS ... and just for the record im not even planning it, those game dont feel appealing to me in any way.
Not sure what you mean by this ... So, if you wanted to get Fighter to your group bcs it needed Fighter, you had to get rid of someone permanently? Why is that a problem? I mean, if your group desperately need a Fighter, but have no use for Rogue, why would you need to keep the Rogue around? O_o
I suspect as much. So trust me, Larian is reusing/expanding many of ideas/structures they established in D:OS2 - pretty much like post Bioware games build on what they established in BGs. That's why so many people complained that BG3 feels more like D:OS3, then BG3.
So D:OS2:
In D:OS2, like in BG3, you can play the game as any of the companions. Throughout the first act you meet and get a chance to try out any of companions that aren't your origin character. You would need all companions as fellow prisoners on the ship, and you would get scattered after the ship is attacked. You wake up on the beach and can find all the companions scattered around the opening zone. There was no camp, so companions that you won't take will stay on the world map, and they will "progress" through the story on their own.
So you have an entire act1 to get a feel for you party. Game doesn't pull any punches so you will probably figure out if your party has issues When you complete act1 you sail out on the ship out of the opening areas, and all the origins join you there for story reasons (you are all sourcerers/have tadpoles and Godwaken/True souls).
Then the connective tissue between act1&2 starts. You are on the ship, and your party is removed. You can find all companions scattered around the ship and you build the final team. Once you are done, the ship is attacked, and all spare companions don't get to survive. You reappear at the end of Act3, where you fight for godhood and they get to compete against you - somehow. It doesn't make sense, but then rarely things do in D:OS2.
Gameplay wise, D:OS2 is classless, so anyone can be anyone really - when recruiting companions you get to choose their "class". With the ship comes the mirror, which allows for changing the apperance of your character, as well to respec them into anything you want. You also can recruit merceneneries if you wish so. Never tried that, but I assume you can leave one of your buddies on the ship and take mercenery instead. How interesting it is then, that in BG3 Larian expands what individual class can do beyond their PnP counterparts - just as if they wanted for any party you build to serve you well.
Companions have their quests that they want you to do, most of them tie into events/factions you will be dealing during crit path. I more or less expect something similar to happen in BG3 - Shadowheart's artefact and mission is pretty clearly tied to the story (with the artifact being transfer to you, so it will be critical, even if Shadowheart won't be around). Laez's kin also seem to be on whatever is happening (and likely tied to Shadowheart's artefact - maybe only one can survive prologue?). Wyll is tied to hell, which is part of the core story, Tiefling is tied to hells. Don't know about Vampire, but I bet his master will be of some importance too.
