@sperkin In my case, with the Model 3 Performance with Performance Upgrade option, some of the energy difference is the tires. Some is aerodynamics, due to lack of Aero wheels. Some is the added weight of the front motor, drivetrain and controller. Some is the energy feeding the front drivetrain, where any added system will have losses. Nothing is 100% efficient, so powering added systems (including the front drivetrain) will lose some efficiency. The latter may be affecting your efficiency, for example.
The energy efficient tires on the Aero wheels have relatively low cornering and acceleration limits, but are probably much more energy efficient.
These are engineering tradeoffs. One can design a system for maximum efficiency or maximum performance. When designing for maximum performance, the efficiency will be lower, and vice versa. Sort of a law of nature and fact of physics, if you will.
If it's any consolation, my first tens of miles in my Model 3 Performance have been over 300 watt-hours per mile, but it's hard not to exercise the insanely high acceleration occasionally. I actually care about efficiency a lot, and realize this is high. But it's also not normal driving. I expect it to be much better when driven more moderately and on long, gentle, Autopilot, Supercharged road trips for example.
I also agree our efficiency will improve over time and driving habits. Your 191 was very impressive on the single motor Model 3. Good driving!
P.S. Any added understeer with the AWD is probably due to the front tires providing some of the forward acceleration due to the front motor. Tires have a total friction limit, often represented by a friction circle. If some longitudinal acceleration is used in a turn, there is less lateral acceleration available. That translates to understeer. It's a reason why front wheel drive cars usually understeer heavily when pushed hard in a turn. You can adjust your driving style to use less forward acceleration in a turn, for example using a different racing line with a late apex. Go to a racing or high performance driving school if you haven't already and would like to learn more.