For example can I transfer from Hero Poker, Carbon to Lock Poker? Or is there only within site tranfering. Or can you transfer across the skins?

No, there aren't any skin to skin transfers at this time.

You cannot transfer across skins unless the skins are owned by the same company. For example Carbon allows skin transfers between aced I believe and one other skin because they own those skins I believe. Main reason you cannot transfer is because each skin is in competition with one another.