In tactics specifically? I seem to remember having the choice to take sides for unagressive non-human during a few missions, for example, which leads command to disregard you, but ultimately allows you to conscript mutants in your team and have unique NPCs to talk to. I think it also changes one element of the ending, with the brotherhood coexisting with mutants and working with them on scientific projects instead of hunting them down. There's that mission with a tribe holding a vault, that can be killed by accident if you turn on the vault's electric systems (which help you in your mission, but dooms the civilians outside) and gets you roasted by your command in the debriefing. The way you deal with missions also change how tribal NPCs react to you if I'm not mistaken. Dialogues with elders from the tribes at the beginning are different depending on how you handled side missions, like taking more risks in order to help a hostage escape. Correct me if I'm wrong, I haven't played tactics for a long time, but I have good memories of it. Not as memorable as the big trio, but still a pretty solid Fallout title, which introduced new gameplay and lore elements in quite a good way.