I have 30 EK Vardar F3-140ER fans and two EK F4-120ER fans in my build and they all operate as described, starting full speed then slowing down.
I did some fan testing
with these fans and an Aquaero, and the most fans I could get to run off one channel was six without tripping the over current protection.
Since I wanted to run up to eight fans per channel, I used four Splitty9s. Then I made a custom harness to run power and ground from my power supply to two Splitty9s per harness and then ran each PWM and RPM wires from the Splitty9s to the Aquaero.
This way there is virtually no power load on the Aquaero, yet I still have full control with the Aquaero.
In the picture here the red and black sleeved wires supply power to the four Splitty9s, and the grey sleeving has both the PWM and RPM wires both going to each of four channels on the Aquaero.