For websites I would check out gamasutra. They great articles like this one https://www.gamasutra.com/view/feature/131556/postmortem_ang.... I know they have some others like on Indiana Jones and Star Wars Ep 1: Racer.
Due to the nature of speedrunning, there is a looooot of details about the game they've investigated and he goes through loads of examples throughout his videos. They definitely reverse engineer the games to figure out how they work so they can do more tricks etc.
The videos are looong but well worth the watch.