I definitely think we're born with it... but all three types and maybe more. We can be born dominant, submissive, or pansexual. We can be born attracted only to the opposite sex, the same sex, or both sexes. We can be born introverts, extroverts, outgoing to shy. We can tend toward monogamy or we can tend toward polyamoury. There are probably those among us who tend toward neither, and have a wholy different perspective of love. And I think it all depends on what our particular genome found to be a success formula.
I also think a lot of our natural instincts are modified by societal mores. So I basically agree with you save that I don't think there's a single formula.
I know I was dreaming dominant dreams from pre-puberty. As I entered the age where I was ready to settle down, I pre-negotiated an open relationship because I already knew I'd fall in love over and over again... and didn't want that to mean I had to "end" my current love and relationship. I'm dominant. I'm polyamourous. Nothing societal made me that way, imo.