I haven't really found the Windows 10 updates to have much of an impact, personally. I have the two Windows 10 Pro computers that I keep up to date now, but even when I had the third (which I put W8.1 Home back on because it was too slow with W10 Home) I still wasn't using that much data.
As we speak my desktop is downloading some W10 updates, so I will update my laptop in a little bit, too, but again, I've not found it to have much of an impact on my data usage. The worst month I ever had was the month where I had to update all three with the Anniversary update, but even then I didn't use more than seven or eight GBs total for the month (including Bonus Bytes).
tkohlman,
You mentioned that you use Edge due to it being like IE, which is what you are used to. Is there a reason why you aren't using IE? It's still usable in Windows 10, and although they aren't going to be releasing any more versions of it, the present one (IE11) is still getting security updates.
Also, mentioned above, it would be a great idea to install Glasswire, which will tell you just what is using data on each Windows computer it's installed on. If you already have it installed from being talked about months ago, disregard this.
Lastly, you said that this problem recently crept it's ugly head again. Have you checked to make sure that your syncing and "updates from more than one place" haven't been on, or at least turned back on somehow. Both of those can use a LOT of data, especially the updates from more than one place if it's set to share with everyone on the net.
Lastly again, regarding Edge, it's still a "work in progress." I, personally, don't trust it. I use IE and Chrome, but Chrome more and more every day.