Some people just don't get along. Like Lae'zel and Shadowheart.
The party is forced to work together because of the tadpole, if it's gone it's the same as your high school classmates. Once high school is over, did you keep in contact with everyone you chilled in class with? Or only the ones you actually had friendship with?
I hope any party locking won't be as dire as Divinity: Original Sin 2. But having to choose between Shadowheart or Lae'zel is pretty cool.
Astarion and Lar'zel seem the most evil aligned, Shadowheart, Gale, and Wyll all seem neutral.
Right now it's looking like half the party versus the other half (pure speculation). Which isn't too bad considering Karlach is another character. So hopefully it will be group of 3 (A) or group of 3 (B), which is a lot more interesting than what happened in Divinity: Original Sin 2.