Do I have to use ICloud Photos, seems redundant if my camera roll gets backed up each time too.

If you have iCloud Photos turned on then the photos are not included in iCloud Backup.

See the following from What does iCloud back up? - Apple Support

When you use iCloud Photos, your photos and videos automatically sync to iCloud so they aren’t included in your daily backup.

Because iCloud Photos will exclude your Photos from your regular iCloud backup of your device, you should then find another way to backup your photos. The same goes for everything you are storing in iCloud (your documents, your notes calendar entries, contacts, etc). For example, archive your iCloud documents and data on a computer, as described here: Archive or make copies of the information you store in iCloud - Apple Support

I am using iCloud photos also on a mac, then my Time Machine backup will save my photos.

If you do not have another device with the same Apple ID, then you do not need to use iCloud Photos. They will still be backed up. Using iCloud Photos can reduce the storage space used on your device by only downloading the high resolution versions of the photo when needed. As for saving iCloud storage space, it won't save you space when shutting off iCloud Photos, since they will be added to the backup file instead.