I don't think Apple turns over encrypted backup files to law enforcement and others. See:
A new report claims Apple backtracked on its plan to end-to-end encrypt iPhone owners’ iCloud backups after the FBI, citing that the move would harm investigations, hounded it not to go ahead with it two years ago. Before launching, the company consulted the FBI and upon objection, it dropped...
www.digitaltrends.com
"Over the last couple of years, Apple has been stern against iPhone unlock requests by U.S. law enforcement agencies. But the company has numerous times turned over suspects’ iCloud backups, giving up personal data such as iMessage chats and call logs.
In the first half of 2019 alone, authorities were able to obtain complete device backups of nearly 6,000 iCloud accounts. In addition to that, Apple reportedly turned over 14,000 accounts in response to secret U.S. intelligence court directives."
That may differ for Notes, but I wouldn't bet on it.