Hi,
i don’t use that tricky registry tweaks for making a profile to default.
Ever tried STRG + SHIFT + F3 in Express Settings to enter Audit mode?
Then do your changes and fire a sysprep:
sysprep /oobe /generalize /shutdown /unattend:c:\pathtoanswerfile\unattend.xml
Make sure your unattend.xml has the copyprofile option enabled!!!
Now take your image.
If you ever need to make changes restore to vm again let it boot and goto audit mode again: sysprep /audit /reboot
I have that parts scripted for my self and can give you that stuff if you need.
Never try to uninstall staged appx apps or you break sysprep, also don’t use O&O Shutup or Stuff like that this also breaks sysprep.
Regards X23