I was wonder how the snes pads work over all I have an Avenue 6 and 3 and mouse. Several games act a little quirky when playing with the av6, plus the pad is huge. I would like the have smaller pad but they seem to go for $25+ these days. If you have an adapter adapter I would be interest in that. I didn't find anything with a quick search of SNES2PCE as you suggested however. I did find a link about modding a NES controller so I may give that a go down the road.
Both SNES/SFC and NES controllers are in expensive. Modern copies vary in quality but tend to be much better than the cheap genesis ones. In the late 90s I would say the position was reversed.