I "feel" that Decompose is useful, so I try to integrate it into my application but I don't understand how "deeply" it should be integrated. Should my application contain • one container component with top/bottom bar and a content slot, • and one component per screen? Or should individual screens also be broken down to a component hierarchy? How can I decide? 🙂 Thanks for any help.

I guess, that depends on the complexity of individual screens. You can start with one component per screen. And then if you feel that a particular screen is bloated, you can extract things into child components. The screen component's entry point usually remains unchanged, its child components are implementation details.