Original Midway Pac-Man on MAME is best, IMO. It's by definition the most "original, authentic" way to play the game. But if MAME stymies you, or if you're looking for the best version to play on a 480i CRT, I recommend the NES port (either Tengen or Namco, they're functionally identical). It doesn't have accurate colors (what arcade port does with NES's weird palette?), but the arcade action is 100% there.

@retropieuser555 It's the Spectrum version hacked to run on Pac-Man hardware, yes. Obviously I know I could run that instead, but I wanted to run this. Happily, I found the ROM eventually and you can indeed play it in Retropie by renaming it to pacman.zip and running it with (for example) lr-mame2003.

@shoebox low voltage can cause big problems, underclocking is one of them. I would skip the canakit power supply as they are one of the less reliable and go straight to the official raspberry pi power supply.