So has any Tesla owner noticed a range difference when driving manually vs autopilot? Or does more efficient driving compensate for the extra energy required for processing?
The current Tesla system does not have near enough computing power for a self driving system. The current AP2 hardware uses NVIDIA Drive PX 2 I think, which is pretty low power, maybe 300 watts? The hardware powering the Autonomous Bolt EV (which is actually autonomous, today) is much higher than that, and the computing power takes up almost the entire hatch back area based on their graphic showing where the autonomous systems are added.
A draw of 2-4kw is a lot, but about half of what the electric heater draws, so it isn't that big. It will definitely shorten the range some, but it isn't like it is a huge power consumer, and I would expect that to drop by a factor of 5 or 10 in a few years. The new NVIDIA Pegasus system looks pretty impressive in terms of power as well. The fact that a Bolt EV has a 60 kwh rated battery gives it a huge advantage for autonomy vs a an ICE as it can easily provide reliable power for the self driving hardware.
If you want to see a huge consumer of power, look how much energy it takes to process a single bitcoin transaction...