@victorlealpontes And anyone else who is still trying to figure this out:
Preface: This doesn't give you full customization of the paywall page. However, if you can't figure out how to change it at all and are stuck in panic mode like I was, this might be helpful!
-Open the paywall page in the website editor, and then select "site styles".
-Edit "Light 1" to your desired specifications.
It doesn't give you effortless and near-unlimited flexibility like with the typical page editor, but it's WAY easier than using code.