I'm not sure of the official way , but can tell you how I found a semi satisfactory cfg.With the caveat that really you should get an r3 to have 1gb all throuput all the time.
On the qos page I use bandwidth allocation with devices with download/upload share excess both ticked.
Turn on congestion set to apply ALWAYS then visit a bufferbloat site such as https://www.waveform.com/tools/bufferbloat then lower your download upload speed (I'm on 1 gig download as well but only 100 meg up) by an arbitary number at a time say 50-100meg and retest for bufferbloat (you might need to reload the page). Till you get bufferbloat very low .
Once you have found that optimum number for me it was 450 down 75 up , change the congestion control to AUTO ENABLE. That way this throttling of your network only happens when you are gaming and when you are not you get the full benefit of your network speeds.
IF you retest bufferbloat with AUTO ENABLE on you will probably get a bad result if someone is not gaming on your network at that moment as it will let your full speeds through so dont let that confuse. Hence me saying find the optimum value with congestion control set to ALWAYS then switch to AUTO ENABLE once found.
If you had an r3 we could have congestion control set to ALWAYS.