Hello guys! I just wanted to update this post because i have some info that it might help some of you.
Basically after i changed my CAT5 for my CAT8, it got an improvement but after keep playing, the issue i had with the input lag it was still there (not as bad as with CAT5), the feeling that i had, it was not just the mouse, it was the game also, the way how the enemies were moving it was not responsive like a floaty feeling, same when aiming with my mouse. I tried to play offline + 4G and the issue was fixed.
As soon as i dont have internet or i connect to my 4G (different internet) the issue was gone, the mouse and game felt responsive how it should be. So 100% is not my computer, also is not EMI/electricity, because during the last 6 months i did everything i could on my computer to fix this.
What i did to fix it is having the router close to the PC with an CAT8 Cable and changed the old router for a new one, this new router is way better and powerful in general compared to the old one. Since i did all of this today, everything feels great so far, i've been playing some CSGO/Valorant deathmatchs, and the improvement of the game its like a new game, i hope it stays like this forever.
Reccaping a little bit, im gonna post here the things i recommend you guys to do that worked for me, and i hope same for you.
1. Buy Ethernet Cable CAT8
2. Having the router close to you
3. Change the router for a better one
4. Install every chipset of your MOBO/CPU. I have Intel and having Intel Management Interface is super important, I had issue with my mouse for a really long time because that driver 3 years ago, when i play with Intel thats one first things i always do, same as others chipsets that you might need when you go into your MOBO website. (floaty mouse feeling constantly)
Things i tried to fix this which didnt work for me. Of course the things im gonna post below it might be the solution for some since our issue might be different.
1. New PC
2. BIOS Settings (Voltages, Overclock, Spread Spectrum, etc, etc)
3. Update BIOS
4. Tweaks Windows
5. Different Windows
6. Different DisplayPort, Bought SAI L-Link, Ferrite Cores, Different Monitor, Mouse
7. Checked RAM
8. Installing different NVIDIA DRIVERS, also installed in a good way with DDU, etc.
9. Differents wall outlets on my house + SAI.
10. Power Plans on windows (also customs)
11. Disabling everything like disable full screen optimizations and this kind of things (like xbox, secundary apps, etc.) Disabling xbox, secundary apps and this kind of things, is more related to have more fps i think, but not related to the actuall issue.
12. Playing on my brothers PC and same issue
And im 100% sure i tried a few more things but right now i dont remember (xD), hope it helps to some of you guys. Have a good night