We are in the process of implementing an integrated Shopify store into our main website.
The goal is everything besides checkout hosted off of Shopify and used APIs to tie it together.
We have everything wired up, but aren’t sure how to add accelerated checkout buttons on our self hosted /cart. Is that possible to get Apple Pay, Google Pay, PayPal, Shop Pay etc to show up on our external cart?
Ooof, that's looking ambitious.
I'm thinking you might be out of luck finding a ready-made solution... Shopify's integration into the checkout flow seems to take a lot of the details outside of your considerations: region-based restrictions, handling edge cases, stuff like that.