Since Tahoe my fan is constantly running

It is possible there are processes running in the background that are using significant resources. Check Activity Monitor, CPU tab (sort by % CPU) and Memory tab (sort by Memory) to see what's running hard.

Activity Monitor User Guide for Mac - Apple Support

Your Mac will not overheat, that's what the fans are for and if the Mac determines the fans are not sufficient then it will throttle back the processors and if necessary shut down before damage can occur.

Turn off the third party Mac fan Control / uninstall it.

A SafeBoot Start up your Mac in safe mode - Apple Support

Login and test. Reboot as normal and test. Caches get rebuilt automatically.

Nothing running hard there (CPU % is cumulative across cores, so for example my M4 Pro chip has 14 cores thus would 'max out' at 1400% CPU usage).

Have you restarted your Mac? See if the problem is present when you boot in safe mode, which disables 3rd party extensions and performs some system cleanup.

Start up your Mac in safe mode - Apple Support