I bought this one, but I and then an extra standalone fan, to have neutral pressure in my network closet, and it has never gone above 30 Celsius.
AC Infinity AIRPLATE T7, Quiet Cooling Fan System 12" with Thermostat Control, for Home Theater AV Cabinets https://a.co/d/0jgj41Ie
I live in a Caribbean island, therefore, mine are always at full throttle 🤣.
It has 2 variable modes:
Smart: varies RPMs based of temperature.
Auto: Off, and turn on based on your settings on at what temp you want them to start spinning, then they go to top RPM.