Tira here, from Shopify.
This is an interesting question. I have some insight I would like to share but I want to make sure that I am tailoring it to your business and needs. Here are a few questions I have to start:
Once I hear from you, I can provide some resources and shed some light on this for you.
Thanks for the reply
1. I'm using Shopify Payments and also want to support things like PayPal and Apple Pay
2. Physical items across a number of a verticals
3. The refunds are being issued because sometimes I want to provide users a discount retroactively. I know I can use discount codes but sometimes people forget to put those in, also I'm thinking of doing some sort of membership where we give you discounts off all your orders (maybe even including past orders)