Hi Steel, welcome to the Ten Forums.
This is a valid and working method but I do recommended it only when upgrading from
Windows 7 if the
ProgramData folder is also relocated. As you know, relocating
ProgramData is possible and works flawless in Windows 7 meaning quite a many users have done it; when upgrading they need to sysprep in any case to move
ProgramData back to C: drive, in which case I also recommend moving
Users back before the upgrade with the same sysprep run using the same answer file.
As a relocated
ProgramData causes a lot of issues in
Windows 8 & 8.1 and does not work at all in
Windows 10, this reason does not usually apply to those upgrading from 8.1 because the
ProgramData is not relocated.
This is the method I recommend. The worst case scenario in doing this is that the upgrade for some reason can't be done and is interrupted, in which case Windows automatically reverts to underlying original Windows version. No harm done.
However, speaking only based on my personal experience with several upgrades, it has worked every time without issues.
The build you will receive, be it upgrade through Windows Update, Windows Store or using the
Windows 10 Media Creation Tool is always the
build 10240, the official release build. All later builds at the moment are only available for registered
Windows Insiders, all earlier builds were preview builds.
Kari