

But about how they would work, I think you can compare any to caffeine:
Caffeine is a drug with stimulant effect that people use to circumvent tiredness. But the stimulus is not lasting, so the person needs to drink again after some hours. And as the body grows resistant to it, and the brain associates the product to the effect, you need to take in more and more, at the risk of getting abstinence otherwise.
As I like to source my own ROMs, those 4 tend to be my primary places to look:
https://www.gog.com/forum/general/roms_obtainable_on_gog_compendium/page1
https://itch.io/games/ (can filter by platform-specific tags for the homebrew ROMs)
https://retropie.org.uk/forum/topic/10918/where-to-legally-acquire-content-to-play-on-retropie/1?lang=en-US
https://github.com/farmerbb/RED-Project/wiki/
Also other places, but most way smaller and mainly found through the 4 above.