Thanks for all of the comments. I don't pay for extra iCloud storage, so I hope that my messages would all fit withinn the free 5gb of space.
Is the syncing pretty quick after the first time? From what I can tell, even without the cloud sync, my messages on all devices seem to update pretty quick. But you are right, if I delete a message on one, it does not delete on the others.
If only that worked with watchOS (and worked reliably with macOS) in terms of SMS sync / deletion.The storage and syncing also means if you delete from 1 device it deletes from all - that may or may not be a benefit to you.
OK, I didn't read that. I looked only at the table. That's unfortunately represented by Apple.A textbook example of reading everything and understanding nothing. From the page you linked:
Messages in iCloud also uses end-to-end encryption. If you have iCloud Backup turned on, your backup includes a copy of the key protecting your Messages. This ensures you can recover your Messages if you lose access to iCloud Keychain and your trusted devices. When you turn off iCloud Backup, a new key is generated on your device to protect future messages and isn't stored by Apple.
The problem is that other users may use the iCloud backup. You can't control that.It's end-to-end. But if you use iCloud Backup the key is backed up. So don't use iCloud Backup if you want to sync your messages and have more privacy.
They're *text* messages. Get a grip and let them go.