Do NOT plug any case fan into the mobo's PWR_FAN connector. That port is for one purpose only. If your PSU has a wire coming out of it with a "fan connector", plug that into this mobo connector; if your PSU does not have on of these, leave this mobo connector unused. What it actually does is feed a speed signal from the PSU's fan to the mobo so it can display it for you and monitor it to be sure the fan is running. It does not control that fan or provide any power supply to run a fan.
Running 4 fans from 2 mobo connectors is a problem. The simplest option is to connect 2 to Molex power outputs from the PSU, although this will run those fans at full speed all the time. If you buy (may come with your fan) a speed controller that slips into the line to each fan, you can set it to some slower fixed speed. Then you plug the other two fans into the mobo's CHA_FANx pinouts. Now, what you get from that may vary according to the mobo's capabilities. At least one of them will be under control of a speed control loop in BIOS that uses a measured temperature signal from a sensor built into the mobo. Maybe both are controlled this way, or maybe the second one is a fixed speed. Read what your manual says. In your case, I see from the specs that one of these two ports is 4-pin, and one is 3-pin. IF you have a 4-pin case fan, plug it into the right connector and it will actually use the special newer 4-pin (PWM) power supply signal there for speed control. If you have only 3-pin fans, plug them in anyway - the connectors are designed for backwards compatibility and a 3-pin fan on a 4-pin port will just behave as a normal 3-pin fan.
BUT suppose you want to connect all four fans in such a way that the mobo CHA_FANx ports can power and control them. Well, with 3-pin fans at least you probably can do this with a few limitations. The key is to recognize that the 3 wires involved are Ground (usually black), + VDC supply (usually red, and varies in voltage according to fan speed the mobo is trying to achieve), and yellow (fan speed pulse signal fed back to mobo to be read). So for one CHA_FANx mobo connector you could take two fans' sets of leads and modify them so that both are fed from one connector. You connect both black lines together and both red lines together to that the fans share the voltage supplied, simply drawing enough current to run both fans in parallel at nearly the same speed. BUT for the yellow lines, leave only ONE of them connected - leave the yellow line from the second fan connected to nothing - so that the mobo receives a pulse signal from only one fan and does not get confused. So at least you could connect two 3-pin fans each to the two CHA_FANx ports and control all of them with whatever your mobo can do in terms of control.
In the case of 4-pin fans, I suspect a similar technique could be done, but I have not done it so I'm not positive. In that case the color coding is different, so you'll have to work it out. But the essence is you must NOT connect in parallel two fan's speed signals, while still connecting in parallel the Ground lines, and + PWM voltage lines, and maybe the + VDC lines (although I believe that +VDC line is not actually used in a true 4-pin PWM fan). One thing for sure, though - do NOT try to connect in parallel a 3-pin and a 4-pin fan. They operate differently can cannot share the different signals.
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