I've put together code for a NES emulator for Raspberry Pi Pico as well.
In my project it can run several ROMs using Mappers 0, 1, 2, 3, 4 and 7 (90% of the games).
It can do 60 frames per second on VGA and emulates APU and PPP perfectly well.
It uses a PS/2 Keyboard as controller (I have no NES controller here with me).
Sound is very impressive and there no glitches on video and backgound game music.
Is it of interest of this community to have an Atari 800/5200 emulated on this board as well?
I'm pretty sure I could get it done in a couple of months or so..
It's very impressive for such a small ARM Cortex M0+ microcontroller.
Video of Castlevania demonstration can be foud at