Xbox one wifi on Asus RT-AC87R

[RMerlin]

My QoS-related issues have all been related to my uplink throughput. I have a 100Mb downlink/12Mb uplink and, for example, Google Drive Sync running on a single pc on my network in the background (without tuning the uplink bandwidth limits in the Windows app) consumes enough bandwidth that my son's Xbox Live connection on his Xbox One goes all laggy. Even limiting bandwidth in the app doesn't cut it alone--it hogs uplink in bursts. Turning on QoS solved this for me, so I am speaking from experience, and I truly think this could be relevant in this case. The overall network load required by many Xbox Live games is pretty low--160 to 300kbps on a test last week--yet it is extremely sensitive to uplink speed, even for downlink speed tests, which you probably wouldn't even be doing unless you had seen the lag I'm talking about.

For that usage scenario, yes, QoS definitely helps a lot. As I said, highly situational.