nvme RAID0 is a pain to get working and you need to know what you're doing, took me ages to figure it out, and its nothing like the instructions tell you, so screw those up and throw them away, there is 3 x "F7" drivers that you need to load (as they used to be known), but basically, unplug all other drives, it will make it easier, just leave your 2 x nvme's connected, id then secure erase them so you will be starting a fresh with them, once done you then need to enable RAID in the bios for your nvme drives, once done, reboot back to the bios, in one of the menu's somewhere you'll see a new option RAIDxpert, this is where you will configure your RAID, enter that, select which drives to use, the type of RAID you want, strip size, label. etc etc, the usual stuff, then save and exit.
Now boot off the Windows 10 USB stick (if that's what you are using, if you're using Windows 7 then you're on your own !!!), accept the license agreement etc etc, once you get to the point where you select the drive you want to install on, you should see your 2 nvme drives, do not touch any of them or delete any partitions etc, they contain critical data, just goto load driver, navigate to the AMD raid drivers folder wherever you put it, the first one to load is RCBottom driver, once loaded you will see all of your drives have disappeared, goto load driver again and load the storport driver, if I remember right this is labelled as RCRaid driver, once loaded you will see one single drive appear, but twice the size (RAID0), now finally goto load driver again and load the last driver RCConfig, once that's done, select the single RAID0 to install windows too, do not format or partition or anything like that, just click next and begin installing Windows, don't forget once done to install RaidXpert drivers in windows to manage your RAID, you can find this package at the link below too.
Get the F7 pre-load RAID drivers from here and extract them to a USB stick:
https://www.amd.com/en/support/chipsets/amd-socket-am4/x470
The file you want is AMD RAID Driver (SATA and NVMe RAID), Revision Number 9.2.0.87, File Size 713 KB, Release Date 10/26/2018
The package to install once Windows is installed and setup is:
AMD RAID Installer (SATA and NVMe RAID)
Revision Number 9.2.0.87
File Size 338 MB
Release Date 10/26/2018