I heard some stuff about Win 7 having very good optimization when it comes to games. Next best thing right now is Windows 10 1709 Update. Disable updates and stay on this version for as long as it is officially supported by Microsoft or untill something better releases.
First thing you want to do after fresh install is opening "Add or remove programms" and uninstalling OneDrive. I'm not sure if 1709 has that shit, but if it does, you def want this it uninstalled asap (I'll explain why later). Then you might want to optimize your Windows to have as little of input lag as possible. Here is a good guide about it.
During the installation you will have an option to put all of your files into a "windows.old" folder. You won't be able to use your old windows anymore but all the stuff you had should be accessible. Uninstalling OneDrive is VERY important because it was made by an absolute degenerate. At some point it thought that it should synchronize my "windows.old" folder with my current windows folder, thus destroying whatever I didn't yet move from it.
I suggest making a backup of the most important stuff just in case.
msg on steam if you have questions