TrueNAS as OS, apps for plex, mc and ha.
hardware:
- intel 12 or 13th gen cpu i3 is good, just not an "f" cpu as you need igpu for plex transcode
- cheapest mobo you can find
- 120gb sata ssd as boot os
- M.2 ssd for apps
- 16gb of ram is enough, but get lots more if you have lots of HDD's
there is a misconception around cooling and power usage. let me clarify; power(watts) = heat, less power means less heat. if your system has lots of hot air coming out then its either doing intensive tasks or its inefficient and taking lots of power to do basic tasks. if the cpu is hot or cold but its doing the same task and drawing the same power then its going to put the same amount of heat in the room. ie a better cooler is not going to prevent the room heating up (technically its the opposite since cpu's can boost).
edit: you can search for n100 alder lake mini-pc 16gb (or 32gb) of ram, they're pretty good for the price. but you'd have to get all external HDD's for your plex library.
smart plugs for devices and shelly CT clamps for home/circuits. all integrated into home assistant.