Hey there, basically because of the gap in Retroarch releases there is a big difference between the released Retorarch 1.9.0 and the nightlies. The 1.9.0 does not have the simple presets option. So we are in a transitionary phase with providing people with presets and tutorials for things.
I added the simple presets option to RetroArch to make it easier to work with these presets and avoid them breaking when the base shaders update. The workflow to work with these presets is different with the latest Nightlies vs the 1.9.0 release. Basically if you have the option of Simple Presets this avoids things breaking on you because you have a reference to the core presets. Then you can add just the texture lines to your simple preset and voila you get a different texture without a copy of the entire preset (which will break on you in the future)
So basically once you have the option of Simple presets it is the feature you should use, unless you want to put your fingers in the machine and make your own presets by actually changing around the passes and such. The problem with this is that your fingers can get caught in the machine and then things can break in the future if the base shader changes…