With the rivets you can pull the mandrel out, it may take a little effort but that's the least likely to risk damaging the part of the rivet that is visible. Cutting the rivet body wouldn't be necessary unless you want it shorter for some reason.Could you expand on what you mean by "cutting the rivets off"? Do you mean removing the mandrel somehow (can it just be pulled out?) or cutting it at the rivet body?
Harry