The Shopify plugin is self-hosted by us and was designed for high-risk merchants or those who, for any reason, are not a good fit for Shop Pay. Technically any merchant can utilize the plugin, but this would be the target market. The plugin is not configured directly in Shopify which is why the third party processing fees are bypassed, instead you and the merchant would work with our development team to implement. The cost on our side is a one-time installation fee of $495, plus a monthly fee of $10. Normal gateway fees also apply. 
Supported:
    • Apple Pay (TSYS) and Google Pay (all processors)
    • Orders can be pre-authorized or captured based on merchant needs
    • Accepts promo codes/giftcards
    • Supports custom shipping details
    • Allows customer login to their Shopify account
    • Payments will display in Shopify portal as well as the gateway (recorded in Shopify as a manual payment)

Unsupported at this time:
    • Any form of surcharge
    • 3DS
    • ACH

Including the developer's documentation that provides some additional details and screenshots below:

https://docs.google.com/document/d/1g9xNrC-jelhIBcAi2yvEm8Rpjr-JGtgBT61z_wdK2S8/edit?tab=t.0