Apps that are disabled do not free up space (other than uninstalling updates as disabling them reverts them back to the original version). They do not keep racking up space, however, as the apps are no longer active, therefore, cannot keep creating files. As for less battery drain, that might help if the apps are constantly running in the background and when disabled, they cannot. Game saves and progress shouldn't be touched BUT that depends on how each app implements their file system.