most will tell you that wifi speedtests can be meaningless.
what matters more is the top handshake speed you may get.
system.log/wireless.log my firetv's handshake at 866 Mbps
while my other wifi devices all handshake with my ac3100
well beyond what they would ever practically need.
with my isp at 100 Mbps and most wired lan hdds at 300 Mbps
wireless speeds any higher really don't yeild anything noticeable.
since we're both on ac3100 & 384.8_2 you may find this interesting;
https://www.snbforums.com/threads/my-ac3100-wifi-settings-any-room-for-improvement.50104/
i try to keep it updated as i trail&error confirm additional refinements.
I agree to an extent. I have 1Gb connection and usually get my speeds I perform test from modem (dedicated machine) and to other devices and give a bit of variance. The device I tested nothing else running except background task had about a 20Mb difference consistently. Again I am more than happy it is finally working just stating what I found.