Also needs mentioning: clustering. I have a years old cluster with none of the hardware I originally started with, but my Pi-hole is still there. Having the ability to migrate guests between hosts is a game changer when you frequently replace or rebuild said hosts. With the right setup, migration can have as little as a few seconds of downtime, or even no downtime at all. You can’t do that with bare metal installs.
Depends what you mean. If I’m understanding you, then no, you’d be dealing with some kind of metadata recursion problem. On the other hand, on my hard drive I have a file detailing the schematic of the drive.
