com.valvesoftware.Steam.Utility.MangoHud VS citra

Try something like this: https://github.com/flathub/com.valvesoftware.Steam.Utility.MangoHud

Took me FOREVER to find it too, found it and PRed it into the mangohud flatpak repo, here you go: https://github.com/flathub/com.valvesoftware.Steam.Utility.MangoHud

Doesn't cover 3DS (Citra)

Another wonderful option is to play Nintendo 3DS games with the Citra emulator. They look incredible. I would go so far as to say that if you're a fan of the console then this is the best way to experience its games, even better than on the original hardware. Again use 3840x1200 @ 60 Hz and full SBS. In Emulation -> Configure... -> Graphics -> Stereoscopy set it to "Side by Side". Also increase the renderer internal resolution to as high as your PC can handle (I used "5x Native"). We'll also have to set the display layout for our resolution and aspect ratio. Unfortunately, this has to be done manually. Browse to %APPDATA%\Citra\config and edit qt-config.ini with this in the [display] section:

After some more research, I discovered that the Citra devs discovered and fixed this issue by allowing the Back button to open the in-emulation menu. This fix was added on Jan 22 2023. When I checked the version of Citra available on the Google Play Store on my phone, it was a very old version from May 2021, which is strange because viewing the same Play Store page on my computer shows it was updated in April 2023... maybe your Play Store version is also outdated? If so, the only solution I can think of would be to install the apk from the Citra Nightly github repo.

https://citra-emu.org/ A 3ds emulator!

You might want to consider compiling it on your Mac yourself, rather than trying to download a build, given the situation with MacOS transitioning to ARM. Beyond that, your question is related ton emulation, not ROMs specifically, so if you still need help, ask on related subreddits like r/EmulationOnMacOS and r/CitraEmulator.

https://citra-emu.org/ just typing the console + emulator on any search engine should give u the best option most of the time

I used the one here (you need a github account): https://github.com/citra-emu/citra/actions/runs/5078058438

There have been several recent changes merged for custom textures. Here is one of the pull requests for example: https://github.com/citra-emu/citra/pull/6452. The slow loading you're talking about was only an issue for me if preload custom textures was enabled.