Only Siphons can become witch-vampire hybrids. Regardless of who's blood turns them. So if Hope turns Lizzie then yes, she'll be vampire who can use witch magic. But if she turned Alyssa, then she would lose her magic and be a regular vampire.

The Gemini were an actual Witch Coven. It just so happened that Siphoners were born amongst their numbers from time to time

there are witches in the gemini too, but I think some are born without magic to balance things, since this witch will become a heretic and the other will die. if hope is to become completely tribe, I think she will not be able to absorb magic, since she is of a different and possibly more powerful lineage.

All witches loose their power when turned into vampires, doesn't matter who turns them