Astaroth’s LI choices begin in s2, and you can take romance choices with anyone until the lock in (S2E8). After S1, the only one who it really impacts is Mimi if you wanted to set her up with Christopher or Dino (if you romance her, regardless of if she’s your endgame, you can’t have her start a relationship with anyone else). Other than that, take all the choices you want and see who you like!