Booting NVMe drive with a bootloader
Solution 1:
Yes, it is doable. It requires manual partitioning though.
As long as the ESP (EFI System Partition) is created in a bootable drive, the OS partition(s) can be anywhere else.
For Linux, selecting the ESP and creating the required partitions can be done during the installation.
For Windows is the same. The installer will use the existing ESP and install in a different, user selected, drive.