Those two fish should get along fine if they are in a large enough tank.
I wouldn't consider either reef safe. Angels are known to pick at corals, I don't believe they are any threat to the CUC though. It will just depend on the individual fish, same for the puffer. Most puffers will pick at/eat the CUC, though the valentini seems to be less likely, since it is in their diet. I've done a good bit of research on puffers as thats why I set up my marine tank, I'm going with a different toby puffer though. The puffer may also pick at corals, again it'll just depend on the individual fish.
I'm putting my puffer in my tank that has few corals and I also have a little bit of a CUC. If the CUC gets eaten I'm not worried and will just replace every now and then, but I will be upset if the corals begin to get picked at. I have a plan to move the corals into a separate tank if that becomes a problem at any time though.