How quiet is the Minisforum?

I'm not sure, but you could always just buy the Minisforum BD790i X3D [1]. Then, you'd be able to choose your own fan and case, and you can make it arbitrarily quiet by selecting a good fan. Early BD790i boards had a bug where losing power causes it to reset all BIOS settings, but they fixed that in later batches. I wonder when they will come out with a 9955HX version. Another good thing about this board is that it has two PCIe 5 NVME SSD slots with active cooling, which is a lot better than most other mini ITX boards out there, including the Framework.

[1] https://store.minisforum.com/products/minisforum-bd790i-x3d

I did exactly this, put it in a 2U case. Fantastic performance, but even with the best Noctua I could put on it the CPU fan sounds like a Hawker Harrier doing VTOL when it's under load. Don't regret the board, but wish my rack was in another room now.

You can adjust some fan settings in the BIOS, like what temperature it starts turning on, the PWM setting when it first turns on, and the temperature at which it hits PWM of 100%. After tuning those a bit, mine is pretty quiet unless I'm compiling with all cores or something.