The fronts are what make up your total barrel length including the back. This means when the front says its 12", it means the back and the front together make a 12 inch barrel. The fronts are also interchangeable with any different back, because the fronts have only one certain threading.
Yes, the ball is still accurate after if leaves the bore sleeve and enters the front. I'm not sure why, the balls come out of there so powerful it stays straight if you have a good paint to bore match.
The difference in the all-americans fronts and the freak fronts is the freak front has like a lip on the end of it whereas the all american is straight. The porting is also a little different between the two.