1. Will I have to regenerate the PayPal button code after I switch to PayPal enhanced recurring payments?
No, that's not necessary.
No, it's only a problem that occurs specifically with ERP. Normally, a Customer going through PayPal checkout, who is signing up to pay you on a recurring basis, will be required to either have, or be willing to signup for a PayPal account of their own, which is what makes it possible for a Customer to update billing information throughout the course of the subscription with you, and it also provides them with a way to cancel future billing if they desire.
But... with ERP, this requirement to have a PayPal account is removed, and along with that requirement, the Customer now has no way to cancel future billing or update billing information ( i.e. updated credit card details, etc. ). The only way to update/cancel billing, is to contact the site owner directly. In short, this is very limiting, and it's the reason why we recommend PayPal Pro instead.