I know Tim_Taylor reported better results with his adapter (~450Mbps if I recall) but for some reason iperf3 is showing only ~200Mbps in my case. I'm using same chip as his adapter (ASIX AX88179) so I'm wondering where the bottleneck is.
I use ASIC AX88178 -> USB2.0 Gb adapter
AX88179 -> USB3
Iperf runs between two network points - speed is depending on more than only the USB adapter
In my case irperf was running in server mode on my NAS with bonded Gb ethernet and client mode on amlogic box.
Running iperf in server mode on my older NAS with simple ethernet -> speed is ~250mbps