Are there non-humans that are in human form?
Yes: Witches, wizards, time lords, zombies, Angels, cyborgs, vampires and veila.
Also werewolves but only when the moon isn't full and perhaps a Bogart as well, if humans/crowds of people/audiences/your inner self, is what your scared of.
It's rare but a patronus can also take the shape of a human.
Also, aliens tend to disguise themselves as humans as well for example : siltheen, krillitanes, bane, gorgons, androvax (species: veil), haemovores and plasmavores.
But none that actually exist outside of stories.
