Hello! Is there a NetSuite native way In SuiteCommerce to allow for our customers to pay Open Invoices Via Credit Card? If so, is this a module or just a feature we have to turn on?

I believe this is a native feature you can make a payment in myaccount section when viewing invoices

Yes, what Bryce says. This is standard functionality and it's something we highlight when we pitch the standalone SuiteCommerce MyAccount product. (It is, of course, included as standard in SC and SCA.)