This YouTube channel describes how a lot of the older games worked, with how OAM worked and so on, here is a link:
https://m.youtube.com/channel/UCwRqWnW5ZkVaP_lZF7caZ-g
It's mostly SNES. I thought they were great videos. Thanks.
I found that channel last night.
This channel also has cool information on how to make Super Mario World glitch.
https://www.youtube.com/user/dotsarecool