Does a person's vision of God come first, or is that vision a result of their religion?
I cannot say. In my religion we do not try do define G-d as having any particular attributes, except as being eternal, all powerful, and incorporeal. Additionally, we are encourage to use science to study His universe.
Maimonides, in Guide for the Perplexed, reminds us of our tradition that creation in Genesis was written as it was because we, as mere humans, could not understand what really occurred. Now, here we are thousands of years later and we are just beginning to scratch the surface of how creation happened.