A: Hi,
1. It is a form-based payment system without a traditional cart or checkout. Customers simply fill out the form and pay. We do support products, but they are specifically for digital goods.

Right now, shipping is out of scope, but we have noted it as a feature request.

2. We offer full hooks support with public documentation, allowing you to create custom options and variations since there is no separate checkout for add-ons.

However, you can offer one-time or recurring pricing and connect any integration through hooks and filters.
Our focus is on simple, fast payment collection through forms and invoices.