First of all, install the NVMe SSD on the M2_2 socket (see motherboard manual). Make a windows bootable usb stick under GPT mode with Media Creation Tool. You will start the BIOS in UEFI mode and disable CSM boot. Also, put Secure Boot on Windows UEFI mode, Fast Boot disabled and AMI Native NVMe support, on.
I hope that what I said above will help you!
You said to use the M.2_2 (secondary) slot instead of the M.2_1 (primary) slot. Is that really what I should do?