How does the Pratt & Whitney F119 achieve its features?
The afterburner is aft of the gas core of the engine in the jet pipe and bypass air from the fan would have already been mixed with the exhaust gases from the core prior to passing through the afterburner flame holders.
Supercruise is by definition supersonic cruise flight without the use of afterburning, so augmentation would not be in use here
Counter rotation of the spools reduces net torque from the spools upon the structure of the engine requiring less metal and therefore lightens it.  The length of the engine is reduced by making use of a single stage, high efficiency turbine rotor per spool as opposed to multiple turbine stages per spool, which would make the hot section of the engine longer.