The difference in character is really only about how you play the quests in game, and the short introduction, with a little bit of flavour text here and there being the only input of the background.

There can still be a considerable difference in playthroughs according to how helpful and *how* you are helpful/selfish. Less if your first play is a 'completion-ish' playthrough, than if you only follow those quests which align with your role playing.