edit: didn't mention resolution - my monitor is 1080p so that's what WoW was running at. No upscaling or anything involved.
I recently picked up my M4 Mac Mini and so far have only done a bit of testing with World of Warcraft. So far I am satisfied with this little thing.
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Retail settings: all High - exceptions are liquid (Good), spell density (dynamic), and outline mode (off) - sliders (view distance, ground clutter, detail distance) at 7.
(please keep in mind these settings could be pushed higher, I just settled on these for consistent performance)
In anniversary area of Tanaris with a decent amount of player activity and NPCs let's just say the expected temperatures, leaning on the side of "too hot", are 87˚ celsius. The hottest parts of the Mac, according to the most recent version of TG Pro, are the performance cores and GPU. Not all P-cores and GPU cores were the same temp, load was on some cores more than others. Ambient temperature, according to TG Pro, was 60˚. At the busiest the framerate averaged around 83fps.
Going into Orgrimmar I'd be conservative and just say the M4 was pushing 160fps. It touched the 240hz limit of my display in the portal room for a couple of seconds but with my graphics settings I cannot expect 240fps from the Mini. I am okay with that though. Of course Orgrimmar is not the most happening place in the middle of an expansion so I headed to Dornogal. Standing in the town square fps went down to like 65fps at the lowest and was struggling to go above 80 in the busier areas. Of course once you step away from the busy sections frame rates climb again. It is worth noting(!) that my tower desktop also struggles with Dornogal in the busy areas and the desktop has a lot more wattage to throw around with a dedicated GPU and CPU with a higher thread count simply looking at the on paper specs. For it struggling is going down to like 80 fps but, again, it has much more power.
Temps in Dornogal did touch the 100˚ mark when sitting in the town square for about 10 minutes. Even when touching 100˚ the fan did not budge from the 1000rpm it had been going at the entire time. Right now I cannot speak to how loud the Mac is at that baseline rpm because my desktop is louder beside it with the hum of fans while churning through Handbrake. And speaking of Handbrake I threw in a 4K version of Revenge of the Sith and with H265, 1080p, framerate same as source, slowest preset, and RF of 23 I watched the temperature of the SOC creep up to 100˚ and exceed it. Only once the P-cores went to 101˚ and 102˚ did the fan slightly spin up faster than 1000rpm. It went to 1260rpm. The ambient temperature started going above 70˚ and the ETA on the job's completion was over 8 hours but let's just say 9, probably 10, to be pessimistic.
Now in both cases of these high temps I did set the fan to max speed with TG Pro. Yes the fan does sound like the Mac is about to take off, and yes the sound itself isn't pleasant. It had a bit of a piercing ring to it. If you plan on really pushing this thing you may be disappointed and/or want some ear plugs. However, in both of these cases the fan did exactly what you expect it to do. For comparisons sake even when my M1 MBP has its fan maxed out the SOC will still be in the 95-101˚ range in Handbrake. With the M4 the fan almost instantly lowered the peak temperatures to a much more respectable 83˚ and held it there. This tells me that the cooling solution Apple has for this new Mini does do the job, however unpleasant that fan noise is.
I didn't try different orientations of the Mini during all this. I can't say if cooling is better on it's side, lifted up, or upside down. The whole time my Mini was sitting on my desk in the normal orientation between my DAC/Amp and right bookshelf speaker. I have to say that I am quite satisfied with this. My first impressions with the hardware now in my hands is basically what I was expecting. In my day to day stuff like opening applications, navigating the OS, using Spotlight, surfing the web, etc etc I do not see a noticeable increase to performance compared to my M1. However, I do notice how much faster the M4 is both in the gaming test I ran with WoW and when using brew. Brew packages and Xcode installed noticeably, significantly, faster than on the M1. Spotlight indexing was done so quickly I initially thought it didn't run at all. My one, depending on your perspective, slightly negative thing I could say about the hardware is just how light it is. Neat how little it weighs but when I first picked it up out of the box I said that it felt a bit like a toy. I have a 2011 Mac Mini I picked up for $25 this past summer that needs a new motherboard and comparing the two I don't find the M4 all that lighter relative to the old design. But I think the older design being physically larger makes it feel a bit more substantial in the hand.