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).