I’ve somewhat updated the control modes page on the wiki but in any case…
In steering mode, the transmitter’s heading stick controls lateral acceleration… which means you’re controlling the G force you feel as you go around corners. This should mean it turns faster at low speeds but slower at high speeds. The throttle stick controls the vehicle’s ground speed. So for a given throttle stick position, it’ll always drive at the same speed even if the vehicle is driving up or down hills.
In manual mode, the transmitters heading and throttle sticks go directly out to the motors (after passing through the mixer in the case of skid-steer vehicles). This mode doesn’t require GPS. The steering response, especially at high speeds will be much larger in manual mode compared with steering mode. The throttle goes straight out to the motors so you’d expect the vehicle to slow down while going up hills, speed up while going down hills.
hope that helps. Thanks for testing.