re: Any negative for having too many CCs open?

Open? No. The act of opening? Yes, but temporary. And you don't want to open a new line shortly before say, a car or home loan application.

Then from there its just an issuer specific decision if they want to extend you more credit, which has really nothing to do with your score at that point.

For example, I have 3 Chase Personal cards and 2 Chase business cards (and something like 10 credit cards total). For me to get a 6th card, I'll probably have to cancel one and replace it with whatever I'm getting, but another bank like Citi would probably approve me for whatever I wanted since I have none with them.