The speeds I am getting on AT&T are much lower than I got with my HTC One M7. I checked it in many cities from coast to coast. Surprisingly, half the time the upload speed is much higher than my download speed. By slower, I mean up to 10 times slower...
This is baked into android. You don't need an app. The AT&T thing you see if probably just their restriction of that functionally. I know on my Moto X if I clicked on the hotspot in the settings it would search and tell me I do not have it turned on and to contact AT&T. With this phone it just activates.
Is there somewhere that we could lookup which towers are on band 5. I am in the process of switching to ATT. I am awaiting the arrival of my OPO to get started. I know that there once was a website where you could lookup tower locations.