I have an iPhone, can not speak to android. My iPhone has a “Personal Hotspot” mode which, when enabled, makes it appear like your basic wireless network on a wireless scan from the router. Not sure if the availability of this function is carrier related (AT&T in US)
When you refer to wireless tethering I am not sure if you mean this personal hotspot or something else.
I have setup an AR 150 for “tethering” with the USB cable. Requires some packages and is covered in another post. My notes indicate problems (V2.13, it cut in and out) though I do not recall. It was not until later that I learned I could use the “Personal Hotspot”, and for travel this became a no brainier (no cables).
If you are leaving it setup, then it may be a different story. I never did a speed test between the two, though tend to think anything connected by cable should be better.
If you are in the US, check your plans fine print. I suspect that all throttle data after some point. I am of the opinion you need about 6Mbps to get a good quality stream for a uninterrupted HQ video (based on Youtube) and on 4g you will probably get about 20 max.
I would probably plug the GLi LAN Ethernet right into your switch and then unplug the router from same. Get the n600 out of the equation. You should not need it and I do not think it will be a fair test. BTW, is the n600 stock or OpenWrt (I assume it’s really a tl-wdr3600)