My odyssey getting my Balance One to reach its 600Mbps rating last year can be found in Are all Balance One’s running half speed on 8.3?. In the end after trying a number of speed test sites, I reported that I “Finally achieved 600Mbps download on Ookla speedtest.net through Balance One; 767/174 Mbps was the high after multiple tests on multiple servers. The key was using the Edge browser (Win 10) instead of Chrome, configuring speedtest.net to Single Connection instead of Multi Connection, and I did not log into the Balance One (the Dashboard display uses CPU). Selecting Single Connection severely limits the upload speeds for some unknown reason. Upload speeds increased to a high of 567Mbps on one of the Multi Connection tests."
P.S. Peplink’s description of how they test router thoughput with iPerf
P.S.S. @Noah_Helterbrand comments on Balance 20x throughput that “Each feature enabled on the router reduces its throughput. In my experience, with all features enabled, stateful routing caps out around 300Mbps. Your biggest offenders are VPN, QoS, and enabling anything on the Content Blocking page.”