> QMC2 is also far superior to MAMEUI in just the customization options alone.
Oh is QMC2 ever amazing, even indispensable IMO. It elegantly supports literally all of MAME's features like no other FE and a whole lot more - if you're a MAME "power user" it's quite essential whenever you aren't using MAME's CLI/internal UI.
The project has been more or less on hiaitus for roughly a year though, given Rene (it's sole author) hit some pesky RL issues. Let's hope he has a chance to return to the project at some point, or pass the torch to an active/interested dev.