You are not correct here because, in my experience 1) memory voltage is set by ET6 once, when you start Windows, no further action is required by the software until you leave Windows, and 2) fan control continues to work after ET6 has crashed and only stops working after the PC returns from sleep if I haven't reloaded ET6 after it crashed.
So it looks that ET6 only passes some parameters (memory voltage and min PWM % and min and max temp for each fan), to the hardware and the hardware itself controls memory voltage and fan speed at all times, independently of any further software interaction (at least until you put the PC to sleep, in the case of fan control).
And there's no other way to control memory voltage and fan speed: if you set memory voltage in the BIOS and then open ET6 in Windows just to check your temps, it will set the memory voltage to the default value (1.5 V) if you haven't changed it, so you have to set the memory voltage you want in ET6 as well, unless you never open ET6. Regarding fan control, you can't set non standard min PWM % and min and max temps in the BIOS as it only allows basic fan control, if you want detailed control you really have to use ET6 (or Speedfan or whatever) to set those values.