Instead of a dropdown for options in Paypal widget, can I use radio buttons instead?

I'm afraid not, the options for products inside of our payment fields can only be displayed as a Drop Down, with the exception being the Quantity option.

Quantity option can be set as either a Drop Down, or a Text Box field.

You can read more about how to configure a payment field in the following guide:

https://www.jotform.com/help/165-Setting-Up-Your-First-Order-Form

If there is anything else we can help you with, please let us know. Thank you.