I am tethering to a MiFi 8000 from my GL-AR750. It connects right away but is slow on the internet (10 Mbps down). I can get 60-70 Mbps down when connecting to the MiFi over wifi directly. Why would the USB connection be so slow?
USB tethering on the router is slow.
Max tethering speed is like 30mbps. But it really depends on phone. I think the driver is not so great.
I tether my iPhone XS and iPad Pro to the AR750 and get over 30mps without any issues. Never tried using WIFI.