iCloud Backup did not restore some internal settings...why?

No, if you have Photos enabled under iCloud settings photos sync directly to iCloud and are not included in an iCloud backup. Actually, anything that has a switch turned on in iCloud settings will be excluded from the backup.

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 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.

There’s a third factor: Some data, such as contacts and notes are not included in a back up unless they are “on my iPhone”; this is very rare. Contacts, Calendar, Notes, and Reminders sync to email accounts, and thus are also not included in a backup. They will be restored when you add back or enable the email account or accounts they sync to.

Yes, anything with a green switch under iCloud will not be included in a backup, but will be restored when you turn those switches on after restoring the backup. You should leave the phone plugged in and connected to Wi-Fi to speed up that sync process.

You can also view most synced data by going to https://icloud.com and logging in with your Apple ID, and also on other devices: Macs, iPads, and Windows (if iCloud for Windows is installed) that also have the same switches turned on. So it’s a way to have the same data on all of your devices.