Hi kev,
If you have the confidence to build one, then you’re expert enough, for what it’s worth i would say W10 is a stable choice, just avoid overclocking, don’t put any software on that isn’t music related, disable as many non essential services, go for win defender AV...keep away from AVG and all those other tsr’s ...I don’t have an internet connection on mine, i don’t need it...as you probably know max out the ram, superfast ssd and read up about all the usual performance related stuff in the environment etc....you’ll know all this anyway...
A cracking GPU won’t help much, avoid 32 bit plugins...
Hope this helps..and best of luck with your build.
One more thing...in the long run I’ve always found it pays to buy a new pc with the top level warranty...everything works..the internet is a lonely place when trying to solve a driver/3rd party processor/bios/audio interface issue that caused by some dodgy plugin code...
Rich