That's good info - speeding things up is always a plus.
The front end is Attract Mode, not MAME. bbegin's image comes with regular MAME front-end/menu plus AdvanceMENU and Attract Mode as proper front ends. I haven't tested AdvanceMENU but Attract Mode works as expected. You can put whatever theme you want in the layout folder and it should work. My goal was to get something like ArcadeSD up and running, which is why I chose that theme.
i'm so out of touch with rpi stuff.
only just got back into mine with the weather turning yucky.
I have a new SSD coming to put this image on.
I think last yr i put killer instinct on the pi4 and it was laggy.
however i didn't realize until later on that mame was running at 1080p
so it might work at a lower res.
or there is this backasswords method.