You certainly don’t need to be a professional CS player to appreciate a higher refresh rate, provided (as you correctly identified) you can run at a suitably high frame rate as well. Sensitivity to this varies, but I’m certainly not a professional CS player yet can easily appreciate the improved ‘connected feel’ and reduced perceived blur that comes with increased refresh rate and frame rate. Refer to our article on responsiveness and the relevant section of our 240Hz monitor reviews (AOC AG251FG and ViewSonic XG2530).
It is certainly a case of diminishing returns. The difference between 60Hz and 100Hz is something most users will find more pronounced than 100Hz to 144Hz (and suitable frame rate), even though the step up is roughly the same. But most users will still appreciate an increase beyond 100Hz, to 120Hz, 144Hz, 165Hz etc. For the best experience these models can’t just promote a 200Hz refresh rate and be done, you will as you’ve identified need a suitably high frame rate. And then there’s the question of pixel responsiveness. I’ve recently reviewed the AOC AG352UCG6, which is a generally cheaper and in my opinion slightly superior (better pixel responsiveness) version of the Acer Z35P. The boost from 100Hz to 120Hz was nice and with pixel responsiveness as it was I don’t doubt if the panel was capable of it a further boost would have been welcome.
As a recent GTX 1080 Ti owner, I think you might be overestimating the demands of the 3440 x 1440 resolution somewhat. With only minor adjustments to in-game settings without obviously compromising image quality it was quite easy to take full advantage of the 120Hz refresh rate. Some flucutation here and there, but that’s what G-SYNC is for. Now 200Hz and 200fps is indeed a tough target to hit, but by making some slight graphical compromises you’ll get there. And by the time those monitors are relased some more powerful GPUs should also be available. Plus, you’ve got G-SYNC to help smooth things out. You’re spot on about cost, though, and I feel that if you’re not interested in HDR capability or the fancy backlight and are happy with something more simple, getting a 120Hz model might be the way to go. There’s also the shortly (ish) to be released LG 32GK950G, if you’re interested in vibrant colours and 3440 x 1440 @ 144Hz. Which could be a nice level to be at. We’ll be reviewing that model when LG can provide a sample, possibly ahead of launch.