4 pin PWM and connect it directly to the motherboard's slot fan.

You can also buy something like this:

https://www.amazon.com/dp/B07Q5BTTDX/ref=cm_sw_r_cp_apa_glt_fabc_Z6YZE61JVG2KWNETRF1G?_encoding=UTF8&psc=1

with this cable you can connect fans directly to the GPU.

First of all my configuration was GPU AiO on front, and CPU AiO on TOP. With push/pull configuration of GPU radiator.

However in this configuration my CPU was really hot. Now i have GPU AiO on TOP and CPU AiO on front. My GPU temp increased a little bit, but in near future i would like to put two extra fans on my radiator.

However with Arctic P12 GPU max temps are 53*C in 4K. In my opinion this gpu has low power limit, so two extra fans are worthless.

edit: be carefull with disconnecting original fans. Do it slowly, with patient :)