In PC computer boards made in last decade it doesn't matter anymore which drive is boot drive. Days when Drive 0 required to have Master Boot Record for all outfit, luckily disappeared in dust. Nowadays you can set desired drive in BIOS and boot from it as you see fit.
Seems we have wrong boot device priority with CSM vs UEFI boot mode situation here again. Windows 10 can install in both modes, but you must boot in same mode which was used during installing. Eq. if you installed in UEFI mode, you must continue to boot in UEFI mode further. And vice versa.
Little hint: When you have new PC with completely empty drive and possibility to boot from USB stick, it is worth to remember which hotkey enable boot menu. Then in BIOS you can set your desired system drive (NVMe drive here) as boot priority drive #1. On restart select USB drive with Windows installation as on to boot. Then you will be able to boot into installing environment. And after installing and restart continue from system drive without BIOS involving. It always works.
One thing about NVMe - BIOS version must be new enough to allow computer to see NVMe drives in BIOS. Recently stumbled upon new B550 board where NVMe drives appeared and became available only after latest BIOS update.