We would be totally fine with merchants using any payment gateway they prefer, however, Shopify calls the shots regarding subscription payment setup.
Shopify decides which payment gateways you can use and what combinations are allowed for subscriptions.
Ongoing is the service you would use for triggering subscription automation. 😅
Example
In this scenario, the merchant is unable to use Shopify Payments.
The merchant would like to use PayPal Payflow Pro as their main payment gateway, but this is not possible as Shopify does not allow it. So the merchant has added Paypal Express as an additional payment gateway so they can be eligible to sell subscriptions. The merchant wants to know how they work together.
Shopify recommendations:
Shopify says Payflow Pro and Paypal Express can't both be active for the selling of subscriptions. (Shopify limitation)
Option #1: Shopify recommends deactivating Shopify Payments and having only PayPal Express activated. The downside might be Paypal is the only option on checkout & they suggested testing out what it looks like (Shopify limitation)
Option #2: If you can get approved by Authorize.net as your primary payment gateway, you can add PayPal Express as an alternative payment and use these two together to sell subscriptions.
Option #3: If you can get approved by Authorize.net as your primary payment gateway, you can use just them alone to sell subscriptions
If you have been denied as a merchant to use Shopify Payments: You most likely won't' be able to use Stripe as your main payment gateway (as Shopify owns Stripe).
If you just want to use Paypal Express, Shopify suggests the payment setup should look like this image below.
This is what Shopify says your Paypal Express might look like on checkout.
