What were the different options with Firkraag? (though I was talking more BG1 than BG2).
I always ended up just killing the dude.
I guess when I consider non-linearity, I don't consider whether or not I allow person X in my group to really be all that non-linear. I am always focused on plot.
For instance, I don't consider Oblivion (or Morrowind) to be a very non-linear game, as it didn't seem like there were many quests that could be done in a variety of ways, and certainly not the main storyline.
I guess your reactions to some NPCs in BG2 does actually have an impact on the game.