The fan comes on when the sensors register very hot.I got one of my two T2 sat on top of laptop cooler powered off the rear T2 USB port.
The internal fan now never comes on unless I'm doing two recordings and playing a video at the same time.
Some years back a user posted that standing the HDR-Fox T2 on it's smallest side (vertically) meant the fan never came on, I have not proved this. It would be easy using the Custom Firmware to monitor the hard disk temperature while testing this out
You would expext the graph to be 'all green' when the Fan package is running, to test the running temperature of the unit when vertical you would need to disable the Fan package or set 'minimum fan speed' to zero.Interesting! I run mine on its side, and the temp, stays bang on 45C.
[It has CF, and I use the fan pkg set to about 45% - I thought the fan was coming on, but the sysmon graph is all green - but is the graph reliable?]
As for the CPU. it does not get as hot as you think.