Shifting into neutral CANNOT, and DOES NOT allow for more controllable nor more efficient braking.
Torque converters "Lock-Up" when the car is being Driven by the engine. NOT upon deceleration. When the brake pedal is depressed enough to cause the "Brake-Lights" to illuminate, the torque converter is taken OUT of the equation.
Also, if operating properly, the torque converter will, in most applications, ONLY "Lock-Up" when the transmission is in Top Gear, and you are no longer accelerating, or barely accelerating when your vehicle speed is around 38-42 mph, and the reduced "Load" on the drivetrain, determined by measuring (engine vacuum, throttle position, current gear, and vehicle speed), then the "Lock-up" occurs. If you continue accelerating moderately to hard, you may find that you're up to 125 mph or so, and the torque converter still will not have "Locked-Up".
So.....having to make an emergency stop from this speed, you'd be wise to leave the shifter completely alone. Engine braking will automatically take place and greatly improve your stability during the stopping process.
"Locking-up" of the torque converter is equivalent to having a taller Top Gear, or another speed. (I won't use the term "Overdrive" because there"s a too universal mis-understanding as to just what overdrive actually is)
As always, there's exceptions.. My old van was equipped with a 4 spd automatic, but the torque converter would frequently "Lock-up" while in 3rd. gear causing the engine to lug. I had the wrong size tires on it.