I did a simple clone job with Macrium Reflect 6 (which had no problem with my 4k Display, O&O for instance still does not work correctly) from an USB 3.0 hard drive dock to the NVMe device. And it worked as hoped for: As a starter I flashed the BIOS to the latest version from Intel. Then in the flawlessly booting restored Windows 10 I then had to update the drivers, most importantly the LAN driver. (I had downloaded them all from the Intel site before as I have learned with recent NUC installs that their update utility is a pain in the ***.)
And finally I had to reactivate Windows. For this I had bought another very cheap Windows 7 Pro 64bit key on ebay (7 Euros!). After some 30 seconds everything was back to normal. But not that overhelmingly faster than with the "old" Samsung SSD, that I had hoped for.