Is the category limited to arcade games, or are you considering adding other systems?

The only major difference of difficulty and gameplay goes more for MS-DOS, Amiga, Commodore64, Zx Spectrum, TG-16, and the rest of ports that will have a separated category in Misc. There is a TG-16 category and run separated already from Arcade.

But in relation to Arcade goes entirely in relation to PS ports, Xbox, Switch, PC (Steam). Therefore, in the case of PS2 the runs must show the Capcom Classics Collection display which is part of the Vol.2 released for PS2 and Xbox.

In short, the Arcade category includes runs of: Arcade of course, PS2, PSP, PS4, PS3, PS5, PC (Steam), Switch, Xbox, and MiSTer.