Privacy: Apple said to not encrypt cloud backup data of your iPhone
See Apple dropped plan for encrypting backups after FBI c0mplained
By comparison, check out this support document from Microsoft regarding how they secure OneDrive data. Their security looks to be state of the art.
When I store important data online, I encrypt it and then wrap it in a second encryption later. Then I store it in an encrypted online vault. Hopefully this keeps my information secure.