For the P8Z77-V Deluxe:

I heard it's not possible to control fans on the CPU fan header by voltage, only PWM. Why is that the case? Are all other fan headers able to control fans by voltage regulation? Is it possible to connect a 3pin-CPU fan to a chassis fan header and let it be controlled by the CPU temperature?

Will the "Fan Xpert 2" software (which is not part of the BIOS) write its configuration into the BIOS/UEFI or do you need to run the software in background in order to make the fan configuration work?