For the first question, i don't know certainly, as the you say, the uesp says they can, or maybe could be that Daedric Princes can reclaim any daedra when they want, maybe some small dispute between princes about it or maybe not, i can't answer 100%, this one sorry for that.
For the second question, it doesn't matter, they are more powerful than regular daedra of course, but they are still minions, and they do as the Daedric Princes command, so the limitations remain the same.