You must realize that if you've already tried a clean windows installation attempt for the 10th time (You shouldve 'already made conclusions after the 2rd install to be honest), some other custom OS is not going to relieve your issues right? It's probably going to exacerbate them further.
LTSC or older version recommendations came from concerns about dwm and FSO stuff that could've changed over the year. Unfortunate that OP wasted some time, but it's literally the only variable that has changed in the past year.
Another thing for me was that the usb driver signed by intel or the microsoft will stick itself to different cpu core to bug (or maybe it's the OEM's .ini settings idunno) try and see if that's a thing for AMD. I am out of ideas other then suggesting affinity policing for bandaiding really. Maybe check gpu-z and make sure gpu is getting x16 lanes. Maybe do some tests with ethernet cables off.
You didn't set your nvidia low latency mode to ultra right? and you don't use any "game optimizers"?
1% 0,1% all was good when I measured it with MSI Afterburner
Yea things were working great e.g. last summer I was playing just completely fine, this 240 hz monitor was perfectly smooth and even better than my old LG 144 hz panel, I can tell the difference.
I've found something interesting, my 1% and 0,1% are really low, what can cause that?
Also have tried 500hz instead of 1000, for mouse and it's slightly smoother
I've been asking for clarification since page 1 but I really think you having unrealistic expectation from your hardware is still a possibility.
Benchmark results in this video is in line with your screenshots on page 1. He doesn't have 0.1% showing but you can see the frametime (10ms is like 100fps iirc). He also happen to run his ram at 3600mhz which is like the bare minimum for ryzen according to some people so that could be the difference.
I get that you could tell the difference between 240 and 144, but have you ever had a exceedingly smooth experience on your 240hz monitor? if so what was your ballpark fps back then? I am repeating this but it could just be that your brother's a better gamer than you are and has all the little things set up properly to avoid these unpleasantries even with slightly slower CPU.
There are resources that can help you squeeze out a few more percent out of your system(power options recommended by others are a good starting point for snappiness and reducing the likelyness of random spikes, and your system will need manual affinity policing too it seems like), but you are claiming malfunction after nothing has changed and people are throwing ideas around that right now. You need to be sure. Could it be an update to bf4 itself that's doing it? Are there people sharing the internet connection with you? What happened last summer lol
No idea how that game works, wanted to taste csgo or even older versions like Source but they have their flaws too I guess. Higher DPI gives me some feeling of extra smoothness, in any game, but I'm not sure how does it work.