In fact, P-51D-20NA should not be as fast as FW-190A8 in turning. P-51D and P-47s are generally less agile than all of its British, German, and Russian counterparts, except at higher altitudes. Then, American planes must have superior top speed and acceleration.
But we have to balance and scale it out, otherwise every American planes in FH2 will be disadvantaged in such small space.