Implementing Payment Provider | GET Manifest

Hi!! I hope everyone is fine, I’m integrating a payment provider, we have multiple payment methods and some of the needs more fields than others. The first endpoint to create for the backend service middleware, is List Payment Provider Manifest

I notice there’s a section named "Available payment methods" (image attached) are these only the values I can use? Or can I send others?

And for example for paymentMethod 1 - can I have certain custom fields? And for payment method 2 can I have anothers one custom fields?