iCloud Photos vs. iCloud Backup Photo Library

With iCloud Photos turned on, then the photos are not stored in your iCloud Backup. They are available on all devices. If you recently switched it on, you may still see photos in your iCloud Backup until it gets removed in future backups.

With iCloud Photos turned off, then the photos ARE stored in your iCloud Backup. The storage amount will just be the photos on your device and any new photos added, or photos deleted, will not be updated on the other devices using iCloud Photos.

gnosislibrarian wrote:

Thanks, Mac Jim ID. iCloud Photos turned off with Photo Library enabled for it to be stored in Backup?

That is correct. If Photos are off at Settings > [name on top] > iCloud > Photos, then they will be stored in your iCloud Backup. The size of the Photo Library used in that backup is only the photos that are on your device.

Yep! you will want your Photo Library enabled. I would suggest to allow most of the items to be backed up unless there is something specific you do not care if you lose its data. That way if your device is damaged or you forgot your Passcode, you will be able to return it to exactly the state it was before.