By putting all the state into a single CRDT then yes, you're going to get conflict resolution across the entire document. But you might also want to think about how big that CRDT state is going to get.

There's no splitting or isolation available here, you need to load the entire Y.Doc to get any of the content of the page. The content of the Y.Doc is opaque bytes, and if you dump it to some other representation (like JSON) then you lose the internal Y.Doc counters that make conflict resolution work.