While they are called witches, these particular inhabitants of the Boiling Isles seem to have far more in common with cultural ideas of elves. Particularly, like in the Lord of the Rings franchise, they are depicted as identical to humans save for pointed ears and, like in the Dragon Prince series, wield powerful magic that they convey through the tracing of spell symbols in the air.
Ultimately I prefer to think of them more as elves as opposed to witches, which are humans who cast spells through prayers to the gods.