If you want to switch to Pi5 fan control via the kernel, you need to connect the fan directly to the board to this fan header. But keep in mind that this is a fiddly thing to do and you still need a script for the power button function of the Argon One case.
It will depends on your distro and the used kernel version if the fan speed currently automatically regulated or not. Normally the fan should only be on, if the temperature is upper the first threshold.
For Ubuntu existing scripts like that, but should not needed anymore if you use a recent kernel version.
I don’t know whats the prefered way to set the thresholds without a selfmade script/service like this to get an own fan control profile. But it looks, that it’s possible via overlay and config.txt too:
https://forums.raspberrypi.com/viewtopic.php?t=359778