Let me just focus on this one: why is refresh rate considered important beyond 60hz?
A framerate of around 24hz suffices in theory to see a series of frames as a continuous signal. At that rate we perceive a series of "slides" not as such, but as a movie. You won't see individual frames beyond that.
But that's not the end of the story.
Even if you don't see individual frames, it may not be enough for an eye to successfully track fast-moving objects. Even in films, in a high-action sequence with a lot of movement, 24fps may not be enough.
Consider an FPS game with a rocket moving right in front of the viewer, from left to right. It will appear only for a fraction of a second. If you are playing at 30Hz or 60Hz, at each frame the rocket will be rendered at a very different location on the screen. When that happens, the brain may still have problems to identify that it is indeed the same object moving, and not just a sequence of different objects with some unspecified velocity.
The above issue intensifies if you have a multiple objects on your screen and your brain needs to track frame-to-frame all of them without mixing them up.
So, how much is enough?
It really depends on your brain and on the game you are playing. How many fast-moving objects are there on your screen? How accurate you need to be in the game?
First Person Shooters are probably the most demanding in that aspect. Not only you need to track your opponents with an eye, you also want to actively track them with your mouse (or whatever controller you have). Moreover, as you rotate your character, the whole world - and not just the moving objects - are moving on your screen at a high rate. When that happens, if you are at low framerates, your brain may be totally lost causing you dizziness...
Especially, if you are a professional in the FPS gaming, where aiming comes automatically to you without any conscious thought, the difference between 60Hz, 90Hz, 144Hz and even 240Hz may be a major difference!
So, if a gamer tells you that he sees a difference, it's probably not because he is an elitist, but because it has a real impact on his performance in the game. Even if that 'see' is not about seeing individual frames.
Other games with a virtual world perceived from first- or third- person view, but without precise aiming, can still improve from higher framerates, but it is not that cruical.
But then, there is a wide array of games, e.g. RTS games with top-down view. For those I don't think you need anything above 60Hz. Your whole screen does not changes as much and you don't need to aim at fast-moving things. Usually.