You always see the same that all others see, the only difference is that the frames in between don't show up.

Do you not understand that an enemy seeing you before you see him is a disadvantage?

On a 128 tick server, a guy with a 128fps, and a 128 hz monitor, vs someone with 64 tick monitor, with a 64 fps (yes I know monitors usually come in 60/120/144, but for the sake of simplicity, just go with it).

1/128 = ~8ms, 1/64 = ~16ms.

At this point, I'd like to make something very clear. The guy with ~8ms refresh rate does not have "only" a 8ms advantage, he can have the full 16ms depending on the situation, or he can have no advantage at all. I believe your FPS is not synced with your tickrates, a quick google search (with no real credible sources) seems to believe this as well.

Here's what can happen. At 0ms, your monitor updates you. However, at 1ms, the other guy comes to peek. His monitor just happens to update him that second. Now, he notices you at 1ms, yet it'll be 16ms before he gets a chance to react. The other guy gets a full 16ms to shoot you. However, as I said earlier, sometimes he doesn't get an advantage at all. So you can get anywhere between a 0-16ms advantage over someone playing with fewer FPS than you, while you can only ever have a 0-8ms advantage on him.

Think about it applies to CS and shooting.

An AK in CS:GO has a RPM of 600. That means it fires 10 shots every second, and once every 10ms. That means 10ms is a very, very important value. If you have a 0-8ms advantage on someone, it's still less than one tick rate and it doesn't really matter. If you have a 0-16ms advantage on someone, there's a chance that you'll get off one more shot before they do.

Have you ever failed to kill someone in a spray when you did 80dmg+? This could have mattered.