@stevefo There was a thread abput the arcade folder allready:
https://retropie.org.uk/forum/topic/253/arcade-folder-how-can-i-find-out-what-roms-use-what-emulators/5
But I will summ that up quickly:
You don't have to use the folder, if you are using mame/fba folders. But if you want to have all roms for mame/fba in one folder, you can use that. But keep in mind that you have to understand the "folder" and how the emulators work first.
Taken from the thread:
When you dump your romset into the arcade directory, you should know which emulator they were built for. You can set em accordingly from the runcommand. If you arbitrarily dump all sorts of roms into it, then good luck sorting em out. I personally prefer to have my MAME sets organized under specific emulators with the best of their respective builds.
And you can also read this wiki page:
https://github.com/retropie/retropie-setup/wiki/MAME
Taken from the wiki page:
So you can have one zipped ROMset for each of these (mame4all, FBA, NeoGeo, advmame) To avoid having several EmulationStation menus for different arcade emulators, all arcade-based ROMs can be placed in the arcade ROM folder, but you will have to specify which emulator each will use from the Runcommand Menu
So basicly it "cleans" the mess of having different folder for different arcade emulators.
But you have to set it up correctly.