The sync client of Microsoft OneDrive and Google Backup and Sync offer a „Files on demand“ function to save local space. Means they delete the local files and keep only a link of it, and download it again on demand, when a file is needed. That works well with Cryptomator also. Of course you’ll have download time if you are using this with very big files and a poor connection. But if we are talking about documents, pictures etc, this might be a decent option for you.
But if you want to use Cryptomator for online backup purposes only (and have local space issues), cyberduck might be an option for you as well.