To me it still looks like the only difference is that the non mutable copy is downloaded to the cache folder while mutable copy downloads to the directory I want. I could delete files from both sets so it seems like it's up to the user to make sure not to mutate the non mutable download in the cache folder.
You can delete locally but it should not affect the remote data.
The data itself is stored in the fileserver. Whatever you do locally does not affect the remote storage, only when creating a new version the changes should be stored (Like when using 'clearml-data sync').