Recover Notes from TimeMachine
Empirically, it seems that the 3 items in
~/Library/Group Containers/group.com.apple.notes/
are updated as a Note is changed, whereas those in
~/Library/Containers/com.apple.Notes/Data/Library/Notes/
are only updated periodically [I cannot find how to trigger those to update, I thought making a new Note may do it, but it appears not.]

My research was actually aided by my old faithful - EasyFind (freeware, no affiliation) - which I set hunting for a keyword in one of my existing Notes. It took quite some time, but found it in the end.