How to edit the layout of the payment section in a form?

Also, is there a way to edit the appearance of the payment integration? Right now, it looks very bland. 

Yes, it is possible to customize the layout of the payment section with CSS code, you will need to inject the code to your form and the guide below will help you with that: 

How-to-Inject-Custom-CSS-Codes

However, if you need help trying to apply something in specific you may let us know and we will be glad to help.