This video (https://www.youtube.com/watch?v=hjWSRTYV8e0) does a really good job explaining frame latency in CSGO and why you can benefit from running at FPS significantly higher than your refresh rate, and why vertical sync doesn't solve it like it should. The game is free now, so I'd highly recommend trying it out if you're doubtful about a smoothness difference between 100 and 250-300 FPS.