Hello! I think that's what for debate, but I wouldn't be surprised if demons are a thing in game, since there is sort of a religious theme. The goblins are just goblins I think.
Most possibly. But there were horned people seen in the last trailer, so there's the lesser chance that the sisters are bull people but super powerful.
The horned people from the Gamescon Trailer have their horns positioned different (the front part of their head rather than the sides like the sisters) so it's just speculation on my part. If Volcano and Galley are demons, then they wouldn't be out of place among the mermaid and griffon boss fights that'll also be in the game
The wolves are common enemies, or at least minibosses. If you reach the end of the Coliseum mode, you can see sneak peeks of some bosses, the Volcano Sisters, the Mermaid, the Griffin, and the Mining Robot