Can anyone suggest what would be the best settings to turn on/off/modify to intentionally cause gameplay to slow down, and in turn provide you with "faster" reaction time?
Maybe setting the Frame limiter to something lower than the emulator's full speed? That should do what you want, I think.
Just enable Frame Limit and set for "Custom FPS Limit" the speed you want
i used to do that on FFX to beat that crazy chocobos races. I set FPS to limit with 20 maximum, which meant the game would now run 3 times slower than usual (for NTSC version). Beat chocobo race in a minute. =P