A 3-pin fan's speed can be controlled ONLY by varying the voltage supplied on Pin #2 (#1 is Ground), from 12 VDC for full speed to about 5 VDC min to avoid possible fan stalling. A 4-pin fan under PWM Mode of control will always receive on Pin #2 the full 12 VDC. In addition it receives from Pin #4 the PWM signal. That fan design includes a small chip internally that uses the PWM signal to modify the flow of current from the fixed 12 VDC supply though the motor windings, thus altering the speed. If it is connected, instead, to a header using the older DC Mode, the fan recevies no PWM signal so it cannot modify, BUT the supply voltage is now varying per the 3-pin fan control system, so the motor still does have its speed controlled. On the other hand, of you plug a 3-pin fan into a 4-pin header that is using the new PWM Mode, that fan receives no PWM signal from Pin #4 (which it could not use anyway, lacking the special chip) but does receive a fixed 12 VDC power supply, so it runs full speed all the time.
The PWM signal on Pin #4 is a lot like a classic "square wave" that is fully either on or off. In a square wave the "ON" portion of the wave is exactly 50% of the time always. In a PWM signal the "On" portion is varied from 0% to 100%, so we refer to its setting as its "% On". For computer case fans, that signal is operating approximately at 20 to 22 KHz, and the voltage of the signal (referenced to Ground) is +5 VDC for On, and 0 VDC for Off. THAT is why some mobos label Pin #4 as "5 V" - it is NOT a fixed 5 VDC line, it carries a signal that is 5 VDC peak voltage in a PWM wave. So you could NOT tell using a voltage meter what is is doing. An oscilloscope, yes, but few have one handy.
The Phanteks Universal Fan Controller does do the conversion from one input signal type into two different types of outputs. Outputs to its 4-pin ports are in the PWM Mode, and outputs to the 3-pin ports are to the older Voltage Control Mode. For Port #1, it indicates, the unit determines which type of fan is connected and outputs there whichever type of signal is appropriate. (Many modern mobo headers can do this automatic detection - it's now common.) Phanteks and a few others previously had a Hub model fully capable of doing most of this. What is new in this particular Hub is that is now ALSO can detect which type of INPUT signals it is receiving from the mobo host header, and adjust its conversion actions to deal with either type. Previous models were able only to convert from PWM inputs to Voltage-controlled outputs, but not the other way.
OP, for your situation since we do not know what your mobo CHA_FAN header is doing, I suggest the Phanteks unit because it CAN deal with whichever is feeding it and you do not need to know the details. But if you do want to know, here is how to tell. You need a 3-pin fan. Plug that into the CHA_FAN header. Boot up and go immediately into BIOS Setup. See your manual, p 2-24 and 2-25. First, set the CHA_FAN Profile to TURBO, then use Esc to return to the Monitor Menu (p. 2-23). There NOTE what it says about the CHA_FAN speed. Hit F10 to get to the Exit Menu (p. 2-31) and choose the Save Changes and Reset. This will reboot your system with the new setting, but you should again go immediately into BIOS Setup. Get back to the Monitor Menu and look at the CHA_FAN speed again - it may be higher now. Note that. Now, go forward to the CHA_FAN header and change its Profile to SILENT. Back out to Monitor Menu, note the speed again, then go through Exit etc. Finally, re-enter BIOS Setup and note what the fan speed is under this reduced-speed setting. It SHOULD be much slower IF the header is using the older DC Mode that CAN control the speed of a 3-pin fan. But IF the header is using the new PWM Mode, than the fan's speed will ALWAYS be full speed no matter what setting you make. That's a sure-fire way to detect what Mode the header is using.
FYI, all those steps into and out of BIOS Setup are there because, when you make a change to a setting, on many mobos it is NOT used until you SAVE and re-boot. On some it MAY be implemented immediately, but we don't know about your mobo.