I have two Sabrent M.2 drives all ready for my new Ryzen build. It would be great to install them both now as my motherboard is still out of the case, as they are a little bit fiddly to fit. It used to be that the best advice when having two or more storage devices was either to either unplug the second drive or not fit it at all until Windows had been successfully installed on the main drive. Is this still the case? Would Windows start dumping files on the second M.2 drive? I'd love to fit both drives now if it's not an issue.
You can leave both drives in. The installer will just put the bios-style mbr on both drives but the efs partition will only be on one.
Why would it corrupt boot? If you're still in bios mode (which I doubt on a board with NVMe), windows installs a copy of MBR on all drives. If in EFI mode (all modern systems), windows creates an EFI partition on the primary drive or uses a pre-existing one. If that EFI partition corrupts then yes, your boot will corrupt, but seeing as OP is clearly exclusively using Windows, chances are Windows and EFI are on the same drive, so everything will pooper out.
I've always found it can save potential headaches later on if I install with just the boot drive connected then add any other drives later. Works for me anyway.
Not my experience at all, in fact my work colleague did it at the beginning of the year with an external drive, the system then refused to boot without the external drive attached... Its a well know thing to happen.
Interesting, I've never had an issue with corrupting windows when replacing second drives and I've never unplugged them during windows install. Just pick only 1 drive/partition to install onto.
It's not only a thing, it's a thing that Microsoft itself doesn't know how to avoid. Like, it prevents you from installing Windows 10 updates until you remove your USB drives 'cos otherwise it might accidentally move the bootloader to one and soft-brick your PC. No, really.
