M.2 NVMe vs SSD

I haven’t taken the m.2 plunge yet but with some newer hardware coming I am considering how to make use of it from a best practice standpoint. The new board & cpu will replace my current KVM host hardware which currently uses an SSD for the host OS. Thinking if the m.2 is best used to run the OS on, or better for storage? I could live without it, but just thinking how to leverage that additional component.

When I say “new”, it will be a asus prime board with a 1Gb Intel nic & a i5 12500 w/onboard video.

Edit: I am totally open to the spinning HDDs as well.