Oh interesting. I might try printing something like that. I'd imagine something like that will disrupt airflow though. You might want to test efficiency of that vs simply turning the wattage down. Would be neat to see a chart with temp, volume, and wattage!

For the Noctua 120mm, youll need to 3d print an adaptor (check ceypto cloaks), I am running the NF-A14 IndustrialPPC 3000 PWM version. There's several flavors of the NF-A14. The normal case fans will probably be quietest but I think they max out around 1800 rpm. There are two industrial versions that max at 2k vs 3k rpm. Generally, volume is directly proportional to RPMs. At 800 watts my fans typically spin around 1800 rpm. I went with the 3k version for longevity amd to give myself headroom if I wanted to run at higher wattage at some point

For the power supply I'm using NF-A6x25 noctua fans which I highly recommend.

Also check crypto cloaks guide. It's very good and was what I primarily followed.