In recent years I read and partially experimented with the latest "graphics" frameworks - but somehow I got lost over a cohesive developer experience when to use which framework (and how to integrate them into a good product). The are amazing "vertical" solutions in these frameworks but I see only few strong stories/app/solutions around them. Does Apple has a "big picture" guide when to use which framework, how to interact between them?
We understand that the number of frameworks can be daunting sometimes. However as you alluded to, we try and offer "high level" frameworks to try and meet developers' needs out of the box, for example, being able to use RealityKit for rendering instead of the lower level Metal.
That said, Apple provides several tutorials and code samples to introduce developers into the various frameworks, e.g.:
Another great resource are WWDC videos, which go back several years in order to build a solid understanding of a particular framework or technology.