I'm surprised so many people are still having issues with this, but then again we are all becoming less tech-literate as time goes on. Although you'd think after the first reports of it happening people would have maybe tried to learn a little more about it.
Anyway, it is possible to (mostly) disable this whole thing without disabling updates or using third party software. You simply go into windows update, find the windows 10 update, uncheck it, then right click on it and select 'hide'. Poof, gone forever (so far, at least). Then as far as that stupid GWX notification, right click on the little arrow on the taskbar that brings up the icons like sound and stuff, click on customize notifications, find the GWX listing, then select to hide it. You can't stop the notification from running in the background, but so far for me it's kept it from popping up anything. You may have to find some sort of 'don't remind' option for the window when windows starts; I disabled mine so long ago I can't remember what I did. All of this is not a bulletproof solution, but so far it has worked for me and my family across a total of six computers (and another two more if you count my friends).
Hope that helps someone. I'm still trying to keep the gwx program from running at all with msconfig; if anyone has any tips I'd love to hear them.