I don’t usually like video documentation of *anything*, but this guided tour of Fuchsia by one of the Google developers working on it was pretty revealing.
Apart from capabilities, they demo the OS’s use of (what looks to be) a content-addressed filesystem, a basic shell layer and dev/build environment, Guix/NixOS like package management, some basic GUI notes, the RPC and introspecting of live system components (including a Plan 9-ish filesystem view) and ends with coding up a component in Rust, along with its API and capability definitions.
I think it’s worth an hour (or whatever playback speed divisor you can handle) of your time.