How can I switch my checkbox to a radio button options instead

thank you in advance.

I have an early bird registration option or a 2 payment plan option.  The selection should be one or the other not both.

I see that you are using Stripe Integration to list your items. You can use the radio button tool instead of payment integration. You can then assign values to each option.

Guide: How-to-Assign-Calculation-Value

After that, use the form calculation widget to get the value or total if the item is selected.

Guide: How-to-Perform-Form-Calculation-Using-a-Widget

Then pass it to a payment field: How-to-Pass-a-Calculation-to-a-Payment-Field

Let us know if you have more questions about this and we'll be happy to help you.