I read up on it but didn't understand why I would use 90% instead of 100%.
To make sure that the limiting factor to throughput is your router. This then allows the router to entirely decide what packets get priority, and always get sent or received with that priority.
And every speed test is different, should I go with the average value of my spdMerlin results, which has daily, weekly, monthly test results? Or go with a different speedtest provider.
I prefer to run manual tests using "continuous ping" under "network analysis" in "network tools". This will display a nice graph of results over time.
I then like to manually down/upload a large file from a known good server that consistently provides good speeds.
Start with no QOS. Run ping, down/upload file. If there is bufferbloat, the ping results will swing widely resulting in large "jitter" values.
Turn on QOS, adjust manual bandwidth settings until the ping results remain consistent and are largely unaffected by down/uploading.
I have observed a need to wait approx 5 mins after adjusting QOS settings, before running the next test.
Where are the WebUI Speed settings?
I'm pretty sure that means the manual bandwidth settings.