We tried as hard as possible to make every religion applicable to every civ. Of course there are some that make mroe sense than others, but you should be able to imagine a version of that society with each religion. That was actually pretty hard to do, we had to scope out all the things that make the civ unique, and aeverything that made the religions unique and not have those conflict.
So I can imagine an Order Calabim, Runes Calabim, Fellowship Calabim, Esus Calabim, Ashen Calabim and Overlords Calabim. The only one that is a bit of a stretch is a Empyrean Calabim. Because Lugus hates vampires and the Calabim are hierachical by nature and the empyrean is fundamentally democratic.
So I dont know what religion is best for them. Someone wrote a Fellowship Calabim story about them as a very primal power. It had a great flavor so I always think aboutt that when I play them. But I can imagine the others as easily.
As for the process of making vampires. Both Moroi and vampires have to be created by other vampires. It doesn't need to be Alexis and Flarous, though of course they started the process. A Moroi has drank vampire blood, a vampire has learned how to consume the soul of another to strengthen themselves.