Strangely enough, your (b) sounds a bit like Cajun and I. When we first met there was a little NRE, but nothing anywhere close to the NRE I have felt with others before or since. Although I don't think either of us consciously tried to hold back the NRE, it just never really revved up, yet we have a stronger relationship than so many I know who have gone through the strong NRE feelings.
I also wonder if the big draw for me to an open/poly relationship is the NRE... something for me to really think about.
Life is about the journey and not the destination,
so what better way to know life
than to wander all the roads and paths set before you.