CP is the abbrevation to Claim Points, these are needed to cashout and they will give you a bonus based on the quantity that you have. For example, 200 CP give you a bonus of 20% more on all your claims.
You earn 1 Claim Points every time you made a claim.
You can have unlimited Claim Points.
The maximum bonus that you can get is 100%
Every time you want to cashout, you will need 200 CP, that's mean you will lose the bonus of 20% in your claims.
No, the email option is only for payments to Coinbase, but don't worry, if you don't have a Coinbase account it will be created at the moment that you cashout.
Note: You can send your earnings from Coinbase to XAPO without fees.