Like pulling down a poorly constructed building and starting construction from the foundation all over again, letting go of a relationship that has no magnitude or direction is indeed a wise move. Starting a new relationship takes a lot of courage. If you do start one and you get engaged, how much of your past should your fiance (or fiancee) know?
If she doesn't ask, I would tell her nothing anout my past relationships. If she does ask, I would just answer the specific question, but without going into much detail. I think she has the right to know what she wants, but other than that talking about ex's is just not a good thing, imo.