When you use a frame limiter or vsync it's a whole different story. The process of actually limiting the frames to the target amount is what causes the the input lag, not the fact that you're running at xx-fps.
Since OP said he's getting 140-300 fps, he's running on unlimited ^^
I know in 3D games games wait for frames to be rendered before taking the input, which usually makes the input lag for 2-4 frames. So if the game lags that input for lets say, 4 frames. For 60fps (16.7 ms per frame x4 ) you'd be getting 66.6ms of input lag. And for 300fps (3.33ms per frame x4) you'd be getting 13.3ms of input lag.
Though I'm not sure if this also applies to 2D games, the inputs could be processed independently from the frame render. But even worst case scenario, the lag you're getting from your fps is completely negligible, since it most likely wouldn't lag for more than one or two frames.
Bigger players in this would be your keyboard itself and the connection. If you're using usb (or lappy kb) you'll have some (very low, like 2ms) input lag, but it increases with the amount of keys you can press at once. An nkro keyboard through usb, which a big chunk of players uses, will have about 6-8ms of input lag. Also having multiple USB connections though the same hub or driver could cause input lag if you end up surpassing it's bandwidth.
How ever, a PS/2 connection will experience less than 1ms of input lag. Most PS/2 keyboards are also nkro.
While were at it, some monitors have more response time than others. It can range from less than 1ms to over 10ms. Most sound devices don't experience lag, but certain options within the drivers can easily create audio lag. If your speakers or headset is USB, you'll be experiencing some audio lag depending on the audio quality. If your headset or speakers gots and external driver, chances are you have about 8ms-10ms of audio lag.
But regardless of the input/output lag you get, it's mostly stable lag so you'll grow used to playing with +/-xxms lag. It'll become second nature to you. So much so that if you ever get to try perfect 0/0 lag, you might perform worst on it... You get o2jamers playing with charts 30ms offsync and they play it just fine haha.
