A little side info. As soon as a fan connection is 4 PIN, it can be controlled. The ASUS Maximus VIII Hero also no longer has a 3 PIN connection. Logically, however, you can still connect a 3 PIN fan without any problems.....
With this mainboard you have 3 fan connections at the top. W_Pump CPU_OPT and CPU_Fan and in addition you have 4 x CHA_FAN. All connections can do exactly the same except for the W_Pump, which has a larger control range than the others.
The labels are only there so that you know in the BIOS which fan is where. DH in the BIOS also says CPU Fan, for example, and so you then control the fan that is on this connection.
The W_Pump connection is actually intended for self-build water cooling systems. The H100i GTX has a built-in controller for the water pump. Since you are using it as a CPU cooler, I would connect the H100i GTX to the CPU_FAN with the 3-pin cable. You can control the speeds there if you install the Corsair Link software. Otherwise, the H100i GTX will run the standard programme.
Grüezi. Yes you can use Corsair Hidro H100i in W_Pump connector. I have only 3 pin fans, but 4 pin mainboard connector is exactly compatible (from above). There is no problem.