So i've been using 20.4.1 driver since last month and can confirm that it doesn't fix this issue.
There is still a HUGE stutter when you are downloading something, refreshing pages or watching a video and downloading something at the same time.
The worst stutter happens if you actually try to switch off ethernet adapter/router so its definitely related to network drivers. Also latmon clearly shows huge lag spikes of ndis.sys and tcpip.sys - the execution time can be over 50ms which creates awful lag spikes and distorts sounds/video and even mouse movements.
I really don't know what to do at this point aside from returning the motherboard. Its unbearable.
I've decided to download 19.1 drivers. It appears that they do not support windows 10 or recent motherboards but its a last resort for me i guess.
#disappointedintel
upd:
Wasn't able to install 19.1. They did not detect i219-v network adapter, probably because they were released a year ago before that motherboard and adapter were available.
#reallydisappointedintel