There are even more issues with the mini M1: Facetime audio will only play on internal speakers, video output is flickering in dark scenes, non-apple BT keyboards and mice are not recognized when you boot into recovery mode, Safari starts to complain on heavy memory use when streaming videos on Amazon Prime, Netflix or Disney+ for a while.

But at least one of your issues is resolvable: there is Ukulele, a free keyboard layout editor for macOS, which I used to create a mapping for a german windows-like keyboard layout. It originated from the time where I was running a hackintosh as dual-boot on a Windows system and it works perfectly on the mini.

Unlike you I had no issues in connecting my existing equipment (Logitech MX keys and mouse, an AOC 4K monitor connected with HDMI 2.0). Although I used a Logitech unifying receiver instead of BT, but just for the issue with the recovery boot screen mentioned above. I found no BT issues on the mini, at least not with a xbox game controller while running arcade games. I guess they are resolved now by a Big Sur update.

And for the I/O ports on the back: welcome to the world of John Ive where design has switched places with style. One has the same issue on iMacs. I ordered an Amazon Basics USB hub to resolve the issue. I also found hubs specifically designed to work with the mini offering you USB ports and microSD/SD-slots and stuff at the front. One does even include a space where you can place a 2,5 HDD or SDD (SATA).

That leaves you with the power button hidden away. But as a sleeping mini M1 doesn't consume that much power, I ditched the option to power it down and up.

The mini M1 does have a fan BTW. Although it seems it doesn't need one. I did not had it running even after eight cinebench multi-core-passes. But according to the ifixit teardown it is there.