Since you hit over 200Mb on your DSL speed test, I think it's unlikely that you have the downstream QoS setup right. Try a MUCH lower figure in the bandwidth setting, like 30Mb. If that works, then keep halfing the difference until you find a stable value that's not losing too much speed.
Set your QoS settings to 90% of your max download/upload speeds ie if you max at 210Mbps down / 20Mbps up, set them to 189Mbps / 18Mbps and then run the Speedtest on DSLReports and check your Buffebloat
Running ASUS RT-AC88U with Asuswrt-Merlin firmware