Virtual copies are pivotal in saving same photo with different processing, without physically occupying disk space or duplicating files, in Adobe Lightroom.
One problem with the application is that the virtual copy data is only saved in the Lightroom catalogue. So if for any reason the catalogue is lost, there is no way to restore the virtual copies.
On the other hand, xmp sidecar files can be used to save the master file metadata and processing, so if the catalogue is lost the data can be restored, apart from the editing history.
One way to save the virtual copy data is to create a snapshot once the virtual copy editing is finished. This will automatically save the same snapshot in the master file, which in the event of catalogue loss can be used to generate a new virtual copy. This method of course requires a manual restoration of the virtual copies, which may be near impossible in one go in a large catalogue of many thousand photos, but at least saves the data to be used when required.