Well, if Paul believed in a "son of David" and he knew someting about Judaism, then he must have held that Jesus was (1) human and (2) had a human father. To have a non-Jewish father (god is not Jewish) creates a lot of legalisting problems. Unlike David, where they could retroactively validate him as being a proper leader, having a non-Jewish father tosses the entire premis into the can. So I would suggest that Paul would have not held with the virgin birth story (which he never mentions) or a non-Jewish supernatural father.
“I've done everything the Bible says — even the stuff that contradicts the other stuff!"— Ned Flanders