I'm not sure that over-focus. Lots of small devices (especially older ones) don't have user-accessible fan speed control unfortunately and even if they do, fans degrade over time. I'm running one of the older NUCs as a home server right now and I'm really tempted to replace it with zimablade. Sure, I could replace the current loud fan, then play around with tweaks to slow it down while preserving the performance. But... I could just go passive instead. It's literally the opposite of tinkering too much.
Disabling the fan is too much work so you want to go to a board which requires you to come up with your own external drive mounting solution? Maybe we just have different ideas on what takes lots of tinkering, which is fair, as I'll take figuring out a software setting over building something or having external mount components.
I'd recommend something like a Beelink over an old NUC though. Tends to be cheaper than an old NUC for better performance and you can just set the fan speed directly in the BIOS on every model I've tried. The larger and thicker the fan the less likely it'll ever run into issues (or make noise in the first place) so cubes where the top is just a large fan work best. Boards with tiny fans are, somewhat unintuitively, very prone to making lots of fan noise over time.
> a board which requires you to come up with your own external drive mounting solution
I've got a tray it all lives on, so no attachments needed. Maybe a ziptie.
> Disabling the fan is too much work
Disabling would be easy, but I can't do that without frying it. Slowing it down means connecting the screen, rebooting into BIOS, adjusting the speed, restarting, collecting data, doing it again to check another setting, ... repeat many times, mounting it back every time. Then set up alerts on high temperature so that when the nearby heater kicks in during winter it won't overheat anyway. So yeah, it's a lot of hassle.
You hold some misconceptions about how CPUs work. Such a box grill not fry even if you disable a fan completely, throw it in an insulated box, and run it at full bore. Modern CPUs have a hard limit on performance but are most often soft limited by available voltage, amperage, or temperature headroom. As the CPU runs faster it runs slower to produce less heat and stay within its soft limits. Both passive and actively cooled CPUs operate by this principle. In both cases it's possible to prevent any heat transfer at all and the CPU will shut down, just disabling the fan on a mini PC outright won't cause that though.
Having even a tiny amount of airflow drastically increases the cooling capacity though. It's really quite remarkable by how much.
The setting procedure, as a result, ends up much simpler. You set the fans to a static speed where you no longer hear them. If that's off that's fine too, but having even a tiny something is a great help in getting more than the e.g. 6 watts of CPU performance headroom the Zimaboard has. If you're rebooting constantly or adjusting things based on season you've done something drastically wrong as my recommendation was set a static fan speed not tune the box for an overclocking competition.
I will admit you have to plug in a monitor... I will also say most consider that less tinkering than even just zip tieing their server and externally mounted drives to things :).
Again, I can assure this is as easy as I'm saying, no need to invent other possibilities, as I have some of the aforementioned boxes sitting next to me in this exact configuration. Some even beefier but dead silent, like 8 core 64 gb ram mini PCs with 3 drives and dual 2.5G nics running quite silently year round and a single trip into the BIOS (which you should honestly be doing even if you're not going to adjust fan speeds).
