By "im pretty sure they are backed up to icloud," do you mean iCloud Photos or iCloud Backup? Are you using iCloud Photos? If so, then Photos is there and not in iCloud Backup.
The thing is, iCloud Photos is not a backup. iCloud Photos is a synchronization service. When you engage iCloud Photos on a device, then the Library on that device is kept exactly the same as the iCloud Photos Library. So, for instance, if you take a picture with your iPhone, it is added to the iPhone's Photos Library, copied to iCloud Photos Library, and then copied to the Photos Library on each of the other devices that you have connected. If you delete a picture on your Mac, then that picture is deleted at iCloud and on all the other devices.
You can't think of iCloud Photos as a backup service, since it backs up mistakes, and there's no way to undo them. Whatever you do with Photos on your device-- it happens everywhere else, all at once. Saving a snapshot of your Library to an external drive is a backup. Backups are static-- dependable and unchanging. iCloud Photos is dynamic, always changing to keep up with a changing Library.
Now, if you turn off your iCloud connection, then whatever you do on your 13 can't change what's at that account at iCloud.com.