IMHO there are alternatives to dropping bombs. The Chinese have no restriction against assassination of heads of state as we do. I would not be surprised if they didn’t already have agents in place in North Korea’s military and government to handle things the way they want to be handled if there was a series of assassinations.
That would by far be the smoothest way to get rid of this problem. Though S Korea, Japan, and China will have a massive humanitarian crisis on their hands once we find out what really is going on up “north”.