The more I try to understand iCloud the more confused I become ...

See if this makes things clearer:

Here is an explanation→What's the difference between device storage and iCloud storage? - Apple Support

iCloud+ has 2 independent functions. iCloud backups, and iCloud sync. It’s confusing because they both have the same name prefix. But they have no connection with each other. Go to Settings/[your name]/iCloud. You will see a bunch of switches (with iOS 16 or later also tap Show All). When you turn on a switch that data type will sync to iCloud. If you do this on multiple devices that share an Apple ID the selected data will sync to all of those devices. 

You can also turn on iCloud Backups. This will back up your phone every night if the phone is plugged in, connected to Wi-Fi and locked.

But note that anything that you sync by the first method will be excluded from the iCloud backups.

AlWeir wrote:

You want to back up you laptop to the iCloud but you don't want iCloud turned on. That is something like a Catch-22. Use TimeMachine to back you you laptop and leave iCloud turned off.

It's an even bigger Catch-22 because you can't back up a Mac to iCloud.

You want to back up you laptop to the iCloud but you don't want iCloud turned on. That is something like a Catch-22. Use TimeMachine to back you you laptop and leave iCloud turned off.