Nobody can tell you that. Even knowing what issues are showing, the configuration of your box, what applications and versions are installed, and what applications do you want to keep, it could take a very knowledgable person several hours to give you an opinion on what to delete.
Whilst CC has a reputation for being a fairly safe registry cleaner, I would advise you not to run Fix All Issues, and remove indvidual entries only when you are sure what they are. I doubt if registry cleaning will make a noticable difference in speed or space on a modern box so don't worry too much about a few stray entries. On the other hand, if you're feeling brave...