Noise and Temperature
Yup, it's very quiet at all times. Our testing equipment reckoned that 400W (53 per cent load) was the turn-on point for the fan when testing at ambient temperatures. What this means in practice is that a Core i7-7700K- and GTX 1080 Ti-based system is unlikely to trigger the fan at all.
The higher-than-normal temperature at 400W is a result of the fan barely switching on, by the way.