Upgrading to Win 10 from USB stick

I wanted to make an USB stick to update several (Win 7/8.1) computers to Windows 10, but the provided Media Creation Tool gave the infamous "Something happened" error (0x80070002 - 0x20016). So I downloaded the .iso file and put it on an USB stick using UNetbootin. While this worked and setup.exe can be executed, which starts a "Windows 10 Setup" I'm still unsure of the results it will produce. Will this update my Win 7 or attempt new install?

I'm aware I have to update first and obtain a valid license key for Win 10 before attempting a clean install. Thats why I'm so hasitant of proceeding at this point, I dont want to mess anything up and end up without a valid license key.

If you run setup from within windows 7 I.e after booting it should provide an upgrade. If you boot directly from the USB stick I think it will do a fresh install however as I understand it from an article I read recently you need to have run the upgrade first to validate your licence however this article offers another option.

http://winsupersite.com/windows-10/windows-10-clean-install-using-media-creation-tool#slide-0-field_images-57241