It seems you know what the issue is and are dealing with it. I do recall at times there were a few specific Windows/netcard/setup issues that required some fairly tricky fiddling with the network parameters for people to get around them.
Switching from WiFi to ethernet cable connect can help if that is possible. Repositioning routers etc. But for the tricky parts, you’d need to look for some posts on things like MTU size or network timing. I don’t have some of those old links on this PC, but it would be posts like these:
https://answers.microsoft.com/en-us/windows/forum/all/wifi-disconnects-once-i-enter-a-game-and-wont/89b7043f-b451-4dc1-8705-2ee900d1387e
Perhaps someone with deeper knowledge of network doctoring could provide some other options.