Yes I am. As for MGK, the description states: "at least one mumble rap song" . MGK'S Binge EP definately quilifies. I actually consider the rest of his stuff to be good, believe it or not
This looks like it was taken from Wikipedia's list of mumble rappers before it was updated to remove a lot of names; half of these aren't actual mumble rappers. I think even a quiz that said "SoundCloud Rappers" and omitted half of these mainstream guys would have worked, although Chance might get thrown onto that one so I'm not sure.