I have the 2015 Sport Tech automatic.
In manual mode, the transmission WILL shift up and down automatically at its limits. This can be really annoying because it may shift right before I shift so I get a double shift!
And it feels as if the gears change harder/not as smooth than regular automatic.
But its great to use for downshifting to keep the revs up going into a curve or about to accelerate up hill.
Soon I will try and use it in autocross where a constant 2nd gear is preferred. Right now the car is TERRIBLE in automatic doing autocross! It lags constantly!!
But for straight ahead acceleration, I just leave it in auto, its does better than me
So, lots of practice would be necessary, and I'm sure your gas mileage will go way down too.
Remember, you are not supposed to coast in neutral with an automatic (it will overheat?).