only way not get input lag is to having an CRT monitor, or playing with real console + CRT TV (and also super everdrive or FX Pak (aka sd2snes). One alternative is real console + OSSC but that has one frame of lag? though its so minimal its hard to notice.
but since you mentioned snes9x. press "video" -> "display configuration" on top bar, then try different output methods, I noticed the default one is laggier feeling than the others. You can also try other emulators like higan, bizhawk..