Unmerged Arcade Romsets contain many Roma clones as well as Roms belonging to genres / categories that you do not want to keep.
This cleaning is to be done on a system which does not have a gamelist.xml and it must be carried out before launching the scrape of the Roms, in order not to recover the media of the Roms which you will finally delete.
This video shows you how to remove:
You can also check out : Filter Arcade Clones