Can I safely remove these MOV files from the OSX SSD?
If CleanMyMac is going to remove the files from their present location, then yes, they will be removed from your Photos Library. 

You would be better off going to "About This Mac" under the apple menu, and on the Storage tab, click "Manage". Then click on "Store in iCloud", and select Photos. 



As a general rule, I avoid all apps that claim to 'clean', 'purge', 'sweep' or otherwise perform housekeeping, as they often can have unintended consequences.