I don’t know. I think it’d be fairly easy to disguise yourself around the galaxy. Wear Mandalorian or Booush armor. In Kylo’s case, grow a beard and cut your hair. In Vader’s, no one knew what he looked like under the helmet. This would be helped with Luke/Rey claiming they are dead.

The problem with immediate death is it isn’t very interesting. Vader and Kylo never confront what they have done. Love should be used as the tipping point back over, but once on the light, it would have been nice to feel some remorse for their actions.