No way I am aware to see the impact of 1 VM other than if a cluster move it off to another node and measure baseline then move it back to the original node and then use that take away the baseline and you have a value.
The value of appliance could be easy reboot for the family if something happens when your away and unable to fix remote.
And the ability to run with a very low power footprint if you only say keep one other all in one box running and keep the big play clusters to use one when needed.
I move back and forward between appliance and VM in my mind, right now it’s a less featured appliance than I want but I would be willing to invest in a supported product (Fortinet 60E/61E or Meraki MX67/MX68 or Sophos, for example of course) to get the low power and feature I want (young children so some traffic blocking etc based on content)
(All those fully supported commercial solutions are let’s say close enough to $10 per week average cost so not cheap but... well actually given my monthly power bill let’s say I had an old not efficient home environment then if it was running 220 watts say, but going to 10 watts I could save that a month anyway, my stuff is not where that inefficient though)