I would not worry anymore about abrupt turning in the Mustang as I would any FWD car as long as you are not accelerating. The Mustang, as is the case for most street cars, is setup to predominately understeer. Throttle application is what separates the FWD and RWD cars in this situation. I have lost the rear only once in my life and it was in a FWD car. I overcooked a corner and lifted off the throttle and the rear stepped out on me. A novice mistake for sure. Any car can spin out, it is foolishness with the throttle that will bite you in a RWD car.
I find the advancetrac system to be quite good. It is not a magic potion and physics will prevail if you really mess up, but it will save your butt when you make minor mistakes. Just leave it on and you will feel it when it kicks in. Learn from those instances when it does and pay attention to what you did wrong.
2013 Red Candy Metallic GT Premium Coupe
Black Leather, 6MT, Comfort Package, Brembo Package, 3.55 Axle
Borla Touring axle back, Suntec CXP 45% window tint, Eibach Pro-Kit, Steeda Strut Mounts, Rear Upper Control Arm and Panhard Bar, BMR Relocation Brackets, Energy Suspension Shifter Bushing