I'm quite sure the Camry has DFCO. How/when it engages is a mystery because you have instrumentation but YOU'RE NOT USING IT!
The ultragauge will show you when DFCO kicks in by showing your mileage sky rocket up since you aren't using any fuel. Get that thing installed even if it isn't calibrated its still incredibly useful. It doesn't need to be exact to really help out. For instance, say you use it uncalibrated and get 50 mpg on your way to work. The next day you get 45 mpg, well at least you know your second day was less efficient and you can probably guess why (hit more red lights, had to slam on brakes, etc). Calibration can come later.
Most efficient highway speed 99% of the time is: slower is better, once in top gear. Take a look at some of the
speed vs mpg charts for different cars for proof.
Coasting in neutral will always be better than coasting in gear. In gear should engage DFCO which means your car is using your momentum to spin your engine around which is going to slow you down faster. If you don't have to stop, put it into neutral. If you do have to stop and know so ahead of time, DFCO is an okay way to save a little fuel.