I found the tip in several places to use RetroArch's Run Ahead option to get rid of input lag. I got the tip to run 2 frames ahead. But after testing the input lag myself I am not so sure anymore.
Look at this:
Images recorded in Kaizo Kindergarten, because it has the input display at the top. On RetroArch with the 'bsnes mercury performance' core.
What I want to know is if a real SNES also shows the B input 1 frame before Mario actually starts his jump. In other words, does hardware SMW have 1 frame delay for Mario's movement?
PS. results are the same for simply moving left and right. the input shows 1 frame before Mario moves.