What advantages gives adaptive quantization...

[Selur]

I set constant bitrate 1520kbits/s (not HQ like earlier) and now bitrate minimum value is 400kbit/s on begginning video and 1000kbit/s in middle

My point. cbr is only constant in regard to VUI settings.

It seems that aq is not compatible with 2pass encoding like constant quantizer.

What? 2pass encoding? NVEnc doesn't have 2pass encoding.
+ 2pass encoding in general doesn't make any sense with constant quantizer encoding. Since if the quantizer is constant there is nothing a 2pass encoding could optimize,...
-> you are clearly mixing up some stuff here

Cu Selur