is it a blue Caribbean tang or a regal tang?? If its a regal I'd have metro and focus on hand for when you add him because I'm sure the stress of the move will lead to a minor ich outbreak.
I also have a coral beauty and it does not nip at SPS. I think of all the questionable dwarf angels, the coral beauty is the least likely to cause problems. If he isn't nipping in the current owners tank then I wouldn't worry about him developing the habit in yours.