Thanks @scoutsam22
The mobo has many other components (e.g. a NIC, DC-DC) with different efficiency. For example, I am looking at the Gigavyte X470 mobos, they all have "gaming" in their name, as are many of the X370. I want to select an efficient board in ATX format (so more sockets). No need for extra speed stripes of LEDs... This is a 24/7 server which does little most of the time.
So, how do I know which boards draw 25w and which 40w?
I will use a 2700 (probably) or 2700X: I hear both use the same power normally but the 2700X can be pushed further when called for.