Does Wishlist Auto Registration require setting up new payment gateway integration?

The short answer is No, you don't need to setup a new integration with the payment gateway. The integration with the payment gateway is done through the regular Wishlist Member integration settings, and the registration process should be done correctly in order for the automatic registration to occur. This is the registration process when using Wishlist Auto Registration plugin: Wishlist Auto Registration does not change the registration process, it only takes the information returned from the payment gateway to auto-register members to the membership site (or upgrade them) so they will not need to fill-in the regular Wishlist Member registration form. Please Note: In order for the automatic registration to occur the regular registration process must be setup correctly.