Just do it like Onedrive/Sharepoint split. Then you could work on things offline and sync with the cloud relay, when you're online again. And you could keep some things entirely offline, if they were particularly private or in draft format. You could download a book to read on ePaper, for instance.

If they sync, then they don't have to have identical content, you just have to mark the stuff -- or the type of stuff -- you want to stay synced. Like, not much point syncing most kind 01 notes, as that's immediately-consumed chatter, but books, articles, technical documentation, git proposals, etc.