M2 850W actually has +12V independently regulated, as crossload diagrams point out. Minor rails OTOH share the same output choke. In that sense it's group regulated, but with different choice of rails than usual group regulated PSUs, which tend to pack +12V and +5V on the same choke.

As for Corsair's semi fanless mode, some users noticed significant whining, depending on fan's position, when it stops.

FYI: You state the Chieftec has a Young Lin fan. It's actually a Yate Loon fan.