Don't know if this is relevant but I had latency issues when my Samsung TV was streaming netflix. Had 100 ms spikes in online games even when QOS was enabled and traffic prioritization was set for my console.
After 5 days of troubleshooting I just moved the slider of bandwidth allocation a little(which was default) and pressed the update button. It seem to have reset something and now everything is good again. no more latency spikes when the tv is streaming.
Which was a weird experience.