What I might do is this.
I can set the BIOS to boot from USB by default which I think is how it may already be set. So I can plug the SATA drive back in and it won't boot to it unless it can't use the bootloader for some reason.
I'll look at MiniTool partition wizard and see if it is possible to copy the Windows partition from the NVME drive to the SATA drive while leaving the rest of the partitions on the SATA drive intact.
I'll then see if it will properly boot from the SATA drive.
Of course if I clone the drive I can set it to be a NTFS disk I think just like I was able to set the NVME drive as a GPT drive when cloning the SATA drive to it so maybe that's my only solution and would have to be something I do perhaps once a week or so.
I don't expect the NVME drive to fail anytime soon, but I'm not fond of my data depending on a USB thumb drive to load a bootloader every time I boot my system. Plus it ties up a thumb drive.
Maybe I'll see if it's possible to put the bootloader on the 1 TB hard drive as it's a quality Seagate that I don't expect to fail anytime soon.