Hi, @3loow16 !
To clarify, you have set up different custom fulfillment services and are wondering if you can use different fulfillment services for different products?
If yes, then yes, you can set which products will be fulfilled by what fulfillment service. Different products can be fulfilled by different services. Once you mark an order as fulfilled in your Shopify admin, each fulfillment service is sent an email with all the order information so that they can fulfill it for you. Each fulfillment service will receive an email based on the products in the order that are applicable only to them.
If you require a more advanced connection than what is available through our custom fulfillment service feature, you will require the use of an app, or you can hire a Shopify Expert to help you build something custom.
Let me know if I’ve understood your question!