I've struggled with this too for my stand alone PWM EK pump. Do I have to set it up differently? I was hoping to not connect the fans to the mobo, etc. I was hoping the mobo would dial down the pump and/or fans. A loud system, but cooler temps (max about high 60c range).

The result was the pump and fans went 100% all the time. So I set the S24 to 'PWM' on the block, and then in the mobo bios I set the AIO port to 'PWM'. I decided to try to get the mobo to do the control. On prime95 I get max 80c if I let ot run for an hour. The results from this were a very quiet system, with the pump and fans only doing about half speed. I set the AIO bios setting to 'auto' as I figured the BIOS would let the S24 do the work. I got rid of that by telling the mobo bios to ignore the CPU fan monitoring.

When I leave this as-is, I get CPU fan error on boot. I set the AIO to 'auto' on the block, so that the block would decide how hard to push the fans and pump. Right now I have the two fans plugged into the S24s fan controller integrated on the rad, and the cable from the pump is plugged into the 'AIO' power port on the Asus motherboard.

Asus rog motherboard fan control