I like
Nancy a lot. It's seldom used where I live; I've only known one, and she was British, given name
Nancy, but she hated it and everyone called her
Nan. I would use it as an independent name, not a nn for
Anne or anything else.
Tracy is so very flimsy and dated. The only thing in its favour is a distant memory from an article on teaching Latin in US schools: trying to relate to the learners, the teacher gave them all Latin names to use in class, and a girl named
Tracy was creatively named Vestigia!