@RK-aus-S To change the default core of a system just go to the Emulationstation Menu (pressing Start), and follow the path:
Main menu - Advanced Settings - Advanced Emulator Configuration
And, choose the console and the options you want.
probably due to the rebuild of the Wiki pages.
Exactly, we are changing the documentation due to several system updates, and to improve access / use for users.
Unfortunately, I have no way of making a quick and simple manual for a "more complicated" system like Arcade.
The most basic thing I can say: each MAME core has its corresponding ROMSET, and using the wrong ROMSET will cause performance problems and / or not even work. (Obviously the BIOS is important, but this is general, it is not something exclusive to MAME.)
I recommend that you research more about it, I know that it is a little complex but it is not as difficult as it looks (although it is not as easy as the other consoles). There are several unofficial tutorials, even on youtube, and there are several topics here on the forum that you can base yourself on.
My personal opinion: if you are not an Arcade fanatic, but just a casual player who wants to enjoy this system, use the Fbneo emulator, which also has a great performance, and is a little more practical. (Fanatics will hate me when they read this, as they care about details of each version of MAME, and which one has the most accurate emulation with the version they played in Arcades, but casual players don't care about that).
See this link (it's in French, but just use the google translator)
https://recalbox.gitbook.io/documentation/v/francais/usage-avancee/l-arcade-dans-recalbox
