Product Delivery Model with Org Manifests

The Product Delivery Model fundamentally comes down to how you bring updates to your users. Packages are just a technical means to modularise a system. It is a (mostly) technical decision which package implements what functionality or if something is deployed as unpackaged metadata. In the end, users are primarily interested in the total functionality of the entire system.

That's what an Org Manifest does: It configures the modules (packaged or unpackaged) that comprise a system. It works best for teams that think of their packages as a software catalogue, and their target org(s) as a selection of installed software from said catalogue. It is designed for a multi-org architecture, where each subsidiary (or business unit) has their individual needs. Org Hierarchies can be identical, or they slightly differ while still sharing most of the software.