Running a 6 node cluster of Pi4s at home now. Did some benchmarks. Long story short. USB thumb drive boot disks are better performance and cheaper than SD cards. Fans are completely unnecessary on a Pi4 with an aluminum heat shield style "case". They do run hotter than with a fan, but they will not be heat throttled with recent firmware.
Example case which does away with the need for fans is: https://www.amazon.com/Geekworm-Raspberry-Computer-Aluminum-...
Admittedly, that's a simple load, but my Pi never gets over 42 degrees C, in a tropical area, averaging around 30 degrees C.