Will disabling and deleting iCloud photos also delete iCloud shared albums?
Shared photos don’t count against your storage, but they do depend on you having an iCloud primary library on one device.
We would need to know how you manage your photo library to give any more guidance. You could be iPhone only, iPad or Apple TV or Windows and Mac in the mix. Lots of variables and a call to Apple support is the best way for you to understand your exact setup if you have questions.
In a nutshell, you could delete all the photos from your online library to shrink it and leave just the shared photos to reduce your bill and toll on the free space Apple gives to each AppleID when they activate iCloud.