Sorry, I must have overreacted because of frustration.
Here are some facts:
I follow and use Mikrotik since version 2.9.27. That is long.
It's not about 200 devices and interference.
Take only one mikrotik wifi AP 2.4ghz in absolutely clean wireless area.
Take 10 different mobile phones.
Do a speed test.
How many will go beyond 22-23 mbit on 40hmz 802.11n ?
One, maybe two. (high end samsung and apple).
Take cheap tplink 802.11n, it will work full speed in same conditions.
It is known mikrotik bug. (now I know it).
How will I change 200 devices, and who will pay for that ?
The investor does not accept project as complete, since it does not work as advertised.
Do you understand the issue now ?