Photos syncd to the cloud from Lightroom Classic are in in the form of Smart Previews rather than full-size originals, and don't count towards your cloud allocation. So, removing them wont free up space.
@Ian Lyons To clarify your reply- Image files Imported to Lightroom (any Mobile Version) WILL occupy space of Cloud storage.
Images synced to the Cloud from Lightroom-CLASSIC Collections Do NOT occupy Cloud space.
There is a method to remove the Full-size files from the Cloud (to achieve more space), and then 'Restore' them to the Cloud as Smart Previews that do not occupy space. See the answer from @JohanElzenga here-