Ohhh that's tiny. I used it literally one time total, just to see if it was booting in the correct resolution. I thought I'd need it a lot, but have had a relatively plug and play experience. The pi boots for about 30 seconds which makes you check the first couple times, but pretty much you'll never look at that.
I *think* you can specify controls. I have 6button layout which is their default. it definitely lets you choose neogeo layout or profiles for fewer/more buttons/deactivate hot keys etc.
I have a reall nice mister jamma rig also- honestly I stopped using it entirely.. the UI and friendliness of recalbox was everything I wanted. I messed with input lag and couldn't tell a difference on recalbox vs mister for my twich fighters like SFA3, so I hardly ever plug it in any more.
The main advantages for me in recalbox vs the mister setup:
- every game uses same default controls, allows bluetooth controller, etc etc. consoles, arcades, whatever. it's easy
- same hotkey for volume up/down, credit, pause, config menus, exit, etc
- every resolution works and has nice modelines. it was easy to play a couple, set my screen, and never worry again
- I've only updated the cores/OS once in nearly a year. Mister was all the time
- It deals with vertical games *mostly* elegantly. Some look perfect in the letterbox mode, some look mildly squished. way better to almost always have them work without screen rotation
- I can connect it to wifi and use filezilla or etc to manage files. I messed with mister's "buildroot" linux shell to make it do these things, but was constantly re-tweaking it with updates
- recalbox has a good blank-screen screensaver. I set to one min for burn prevent.
- it will background play mp3s from a playlist. I have either ambient 80s arcade sounds (hah!) or an 80s playlist in it
- retroarch lets you go completely apeshit with custom config/video. I even have vectors looking tolerable on it
- backdrops and overlays! space invaders with the planetscape, discs of tron with the projection, etc etc
- sound samples. Q*bert swears! no missing sounds. you can choose various cores and pick/choose for perfect. I would be willing to spend hours to get the "knocker" workin on Q*Bert again too

- laserdisk games/daphne!
- has a "kiosk mode" for when the nephews come.. I can pin it on a particular game and disable hotkeys until I press service button after opening with key. Give them a bucket of tokens and park it on a multiplayer arcade.
My to-do list yet..
- some per-game configs for sound level. You can nicely normalize them so a few loud ones don't require volume changes.
- watching for the next update as the SDL port of apple ][ emu broke in current..
- a few more plug-in controller tweaks.. I have a spinner (discussed in this thread!) that works but not quite "dialed" in perfect
- consoles/computers.. I have more exploring to do. Do I want Dark Castle working with kbd/mouse on my jamma rig? I am dumb enough to say yes and spend hours getting it all working with a USB adapter and original single button bus mouse/kbd..
Stuff I will rarely plug Mister back in for:
- acorn archimedes
- pong!
- some more obscure computer cores like TRS-80, commodore PET, etc

- apple ][. Hoping they release a working binary again on recalbox soon- it worked before last update!