I have to say that I know of no really objective method by which to test the following but… I thought I’d share my observations on fan noise in EOS running my window managers. Here’s my story, and I’m sticking to it. 
I have been running hlwm on eos for a week or two. I am quite happy with both. FWIW hlwm (HerbstLuftWM) is one of favorite window managers. Today though, I thought I’d change things up a bit and run dwm (in the exact same user-space). To my surprise, the fan noise on my machine when running dwm has more than doubled (this is just my subjective sense). It’s not a problem but simply a curiosity.
Chime in if you have a similar experience.
When I spin up i3wm and bspwm on my machine & user-space, I will, if my old brain remembers, update with any notable experiences. I’m certain the forum’s anticipation is palpable… 