Excellent article and list of projects. Thank you for also including a list of compatible USB C cables for the Pi 4 since it has "issues" with the USB C port.
The Picade is a very fun project. The screen is excellent quality. The kit has been improved over the initial release some. The instructions have not though. The reviews mention needing to use videos and such and this is true. Not a big deal though, it's easy enough to figure out.
I will say N64 emulation on the Pi through RetroPie is, well not a good experience. Generally it is going to take tweaks to make it work smoothly. Gameboy Advance can also struggle in places. NES, SNES, Sega, TurboGrfx, Atari, Gameboy, even actual Arcade stuff plays smoothly generally out of the box though on RetroPie. (I've been using Pi 3 B+ s for this, haven't tried a 4 yet)