Most of the audio and video settings can be edited in two ways.
1. Within emulationstation there is an “Input Configuration” screen, there is an option called RGUI, this is the retroarch configuration menu. Here you can edit pretty much everything, just remember that you need to “Save Config on Exit”
2. Edit the actual text in the .cfg file.
Many of the emulators are configured with one file, this file is called retroarch.cfg (and is the same one that is edited with the RGUI menu). The filepath is > /home/pi/RetroPie/configs/all/retroarch.cfg
Now you can edit this file within the terminal or you can connect to your P remotely and edit the file.
So far so good, now you need to know what to edit, basically you want to DISABLE video shaders.
The config line is
video_shader_enable = " "
Between the quotation marks you can have two settings, “true” or “false”, basically on and off.
Now thats not all!
If you look in /home/pi/RetroPie/configs/ there is a folder some of the emulators, like nes and snes.
In those folders is another retroarch.cfg, what this one does is allow you to make additional changes for each individual emulator, so you could have filters and shaders on one, different audio settings for another, or a different joypad configuration for all of them, this makes customisation better so if you are having problems with performance in one emulator you can turn everything off, and in another turn everything on.
Go check each retroarch.cfg file for each emulator you are using in their respective folders. They may have video shaders enabled in that file, disable them if you want to turn it off.
Anyway I need breakfast, good luck!