Maria - I'm very well aware of the issue with wireless support; that doesn't help solve my problem. What is becoming apparent is that there is a huge hole in the Parallels configuration options that haven't caught up with Win 10. I can't believe I'm the first to bring this up - metered connections aren't all that unusual (though I've never had one at home). The only option I see now is to shut off the VM network connection entirely. I only use the VM for running Quicken Windows and the account downloads don't use a lot of data, but if I turn on the connection for Quicken, Windows will start downloading updates and I can't allow that. You have me between a rock and the ol' hard place.
And btw - according a tech at VMWare, Fusion does not have this issue as you have the option to select "Wi-fi" for your Win10 VM, which gives you the options you need to limit downloads on a metered connections. And also btw, metered connections aren't just limited to wi-fi. (I haven't tried Fusion - yet - so I can't verify this claim.)