if you want to change your CID, do it via SEUS, and again the only way is up: 49 -> 51 -> 52

if your phone is fully unlocked, you don`t have to worry about anything: higher means better, no bugs and you can still flash&have fun with it aka customization

if your phone is locked you shouldn`t move so quickly to a higher cid.

someone correct me if I`m wrong :)