Nostr and bitcoin share taproot as identity.  That is the powerful thing, and the synergy at the intersection.

The relay part shows a proof of concept, of what can be, but relays dont scale much beyond rapid prototyping.

Notes and other stuff, bitcoin, taproot are all good.  The intersection is hugely unexplored.  There is a whole financial layer there, smart contracts, derivative, streaming sats, gamification, over and beyond anything lightning can dream of.  It's an untapped gold mine, and I know you're going to figure this out!