long-range nukes would be in huge missiles that are super slow and super inaccurate, they would be shot out in the sky faaaar faaaar away from their target, in this case somewhere in the middle of the pacific ocean.

However, if north korea decided to launch a nuke to south korea by one of their short range missiles, there's gonna be guarenteed lotsa of casualties on one side of the other, whichever side it blows up on