Worldbuildy notes.
Twelve (formerly thirteen) family bloodlines. They’re massive, spread all over the world. Almost all of those with the bloodline are just carriers. Magic only manifests in queer guys, and even then only in one or two per family per generation. When a kid comes into his powers, an older witch somewhere loses his. Most of the time. It’s magic, there are lots of exceptions.
Yes, trans guys can be witches. The magic is proof enough that nobody will squawk about it (see above, re: sometimes exceptions).
The religion associated with witchdude PCs is wicca-esque, centered around a triune deity manifesting as Warrior, Father, and Sage. Any given witch may or may not buy into it or be particularly devout.
There are other witches in the world with their own types of magical powers. Witchdude PCs may or may not ever run into any of them. Different sects keep their distance from each other to avoid conflict whenever possible. So yes, women can be witches. You’re just not playing one of those.
Witches make binding oaths to one another to form covens. A witch who breaks his oaths is branded a warlock and outcast. Warlocks are treated about like you’d treat Nazis; the most infamous warlock hunted down and killed his entire bloodline (no small feat!), which is why there’s no Thirteenth House anymore.