SF Stripe doesn't need SF-Core. It adds basic Stripe API key management, reports on transactions (no secure payment data stored on site), and a new Form Action.

You can add a form to a template for 'on-page checkout'. Add prices to a custom post type and a SF Stripe button - click and go to the Stripe Form to pay. Add a manual, fixed price. Add a Select dropdown of products and prices and let the user choose.

The payment info stores name, email and safe transaction details which you can later review and export. You can also store any of the form fields in a Notes section. You can set the API keys in wp-config to keep them secure.

 All prices and transactions are guarded by server-side checks, making the form secure and ensuring dubious people can't tamper. There's also a webhook to ensure that if Stripe takes payment, but the form doesn't submit - we can still record the transaction and pull the data later.