In any case, you can leave the Gith and Shadowheart at the beginning or move them and then they suddenly reappear somewhere later in Act 1.
Gale can be rescued from the stone or not.
I haven't found any other option so far. Wyll will come to you either way, at least if you take Karlach with you and don't kill him.
I haven't tried it any other way yet. For example, leaving him standing for now, killing Karlach anyway and then seeing what happens to Wyll.
I haven't tried much else with Karlach either. One method you could try would be to kill the Palas straight away without talking to Karlach and then not go to her but see what happens. But then you shouldn't approach Wyll about it either. Whether that would just fizzle out is a good question and would have to be tested.
I also don't know whether Astarion will stay on the beach for all eternity or whether he'll get lost somewhere else if you don't speak to him.
What happens to Halsin if you simply don't visit him in the fortress at all, but just play things out until the fight in the grove? Whether he then dies in the dungeon or simply appears is a good question.
That's all there is at the beginning. The rest of the companions will appear afterwards.
I think it's quite successful if you fill companions with life in such a way that they reappear in a situation later in the game.
