But I personally prefer a story that withholds that for a while so that when the characters do start acting out of their own self-perceived character as a result of their encounters with each other, you really feel the impact of it.

Strong agree! The book I'm reading right now, Rebel of the Sands, has its issues but it's great for showing the heroine being ruthless to people so she can survive - including drugging, robbing, and leaving the hero at one point - so it's bigger when she stays with him and massively risks her own life.