Also, is there a way to utilize the API/Admin Dashboard? Can I clone that functionality in isolation? I am decently new to forking/cloning OSS, so I want to make sure I am doing it right.

You can set up an app that has the api, core, and backend without frontend, if that's what you're looking to do.

That is indeed what I am looking to do. I don't need any custom functionality YET, but we have the potential to get into some sticky inventory management/fulfillment/shipping situations where having the ability to add on is necessary. This should set us up nicely.

Yeah, adding to and customizing the admin is a normal thing people do in their apps.