Interesting - I'm used to desktop/workstation hardware where 80mm is the smallest standard fan (aside from 40mm's in the near-extinct Flex ATX PSU), and even that is kind of rare. Mostly you see 120mm or 140mm.
Yeah. In a home environment you should absolutely use desktop gear. I have 5 80mm and one 120mm PWM fans in my NAS and they are essentially silent as they can't be heard over the sound of the drives (which is essentially the noise floor for a NAS).
It is necessary to use good PWM fans though if concerned about noise as cheaper ones can "tick" annoyingly. Two brands I know to be good in this respect are Be Quiet! and Noctua. DC would in theory be better but most motherboards don't support it (would require an external controller and thermal sensors I think).
> Those 40mm PSU fans, and the PSU, are what they are replacing with a DC bus bar.
DC (power) in the DC (building) isn't anything new: the telco space has used -48V (nominal) power for decades. Do a search for (say) "NEBS DC power" and you'll get a bunch of stuff on the topic.
Lot's of chassis-based system centralized the AC-DC power supplies.
