The fan noise can be quite annoying if you don't live above a club in Ibiza... ;-)
However, I recommend the Noctua NF-A4x20 FLX (40mm, 2 or 4 pieces), because they are 10mm longer than the A4x10 and can therefore push more air through.
And rather four pieces, because Digitec earns more that way...lol No: Because they can then run slower = quieter. The switch measures the temperatures of the components and controls the fans, which is easy to see.
Noctua NF-A4x20 FLX (40mm, 1x)