I use Alpine Linux for all my dockers, small and fast.

2.5" disks are SMR, you don’t want that in a raid.

Unless you have use case for that much horsepower I would suggest, like others here, buy a mini PC as a start and if you need more down the line buy a second one. They are cheap, fairly quiet and don’t use much power.

It’s called power supply idle control, worth a test.

There is an issue with ryzen and certain PSUs that when it goes to idle it pulls so little power that the psu thinks it’s off and kills the power, it can appear as a hang. there should be an option in the bios to change it to “typical power” or named something similar.

Yes it’s normal, I sometimes use that to disinfect my ears after diving and it sizzles a bit.