As far as I can remember NWN1 and NWN2 were unrelated storyline wise in the terms that is wasn't the continuation of the same character. This didn't bother me personally. I feel the same about BG3, in that it doesn't need to be part of the Bhaalspawn Saga. The overall story for me is about the city itself as opposed the individual characters. On saying that however, I like to play the same character through all the D&D games whether that be IWD, BG, or NWN. I tend to blur the timelines a little so less time has passed and come up with reasons why they are back to lvl 1 again.