These can always be downloaded again at a later stage if needs be. From here you can remove any movies you have already watched. The second option ‘Optimize Storage’ relates to iTunes or movie files that you have stored on your Mac. Any recently used files in your ‘Documents’ and ‘Desktop’ folders will be moved to iCloud.
If you have fast and reliable internet connection, choose the ‘Store in iCloud’ button. Next, click on the ‘Storage’ tab, then select the ‘Manage’ button. Once of the ways to streamline your file usage is to go to ‘Apple>About this Mac’. Even though macOS 10.13 is very efficient when it comes to using files, as time goes by temporary data and third-party applications can decrease the speed of your machine.