Earlier quoted context omitted.
I didn't know HA had plugins like this, seems weird, HA itself is one of these things, not some sort of parent thing to which they're deployed. That's how I see it anyway.
Depends on how you're running it. When I was running hass.io on a RaPi, I used a few of those plugins (including PiHole). Now that I'm running HA in a VM on a bigger machine, it makes more sense to run those services as separate VMs alongside it.
I suspect a single OS on metal with each of these in a Docker container would be more efficient, but I haven't played with containers before.