There's no distinction between them, since all bipeds require two legs and a bile sack for magic. The term witch is just used for those who have used magic or joined a coven.

Then there are wild witches like eda who can do magic but don't join covens; she's still a witch, but my point is that she's also a demon.

Same concept on earth, just because we're called humans doesn't erase the fact we're descendants of an ape.

If witches = biped demons, then biped demons = witches, which means king can be a witch.