And now you are my hero! I have a Pi 4 as well (4 GB) but are patiently waiting for a complete and tested image to appear on ArcadePunks. I will stick it into my Roshambo Retro Gaming case (SNES lookalike) but that probably need some modification as it now houses a Pi 3B+
I've been using Lakka ( https://www.lakka.tv/ ). You have to download an Alpha version and there are bugs. I'm waiting for RetroPie ( https://retropie.org.uk/ ) to catch up. That's my go to. I like their interface. The Lakka interface is very similar to the PlayStation OS, which I have and I like, but it is far less intuitive than RetroPie.
Once it is all said and done, my brother wants me to make him one. I told him I'll set up his SD Card and mail it to him. he can buy the Pi board and a case and put it all together. That's the easy part!