It’s going to change the length of throw at the pedal. If you like a real “short” pedal (applies quickly and rapidly) put it at the bottom. If you like a “long” pedal (more travel) put it at the top. Since it’s easy to change try it both ways back to back and see what you like. I’m most comfortable with a very short pedal but I’ve got a buddy who likes his the other way. I can’t hardly drive his kart. It just seems as though you push and push and push then they finaly grab.
Placement will effect the needed pressure but it’s very little and I’d be surprised if you’d even noticed the difference.
The connection point will make considerable difference on braking power along with the change in throw as correctly mentioned above. The highest hole on the arm will give most braking power. The opposite holds true for the connection point at the pedal.
No offensive to Jim, but in my experience, the position of the rod upon the master cylinder lever makes a considerable difference in brake effort and feel. It’s basic mechanical advantage stuff. The higher you go on the lever, the easier it will be in terms of over-all force required, but the pedal will have to travel farther. Due to the need for more pedal travel on the higher point, drivers tend to report an increase in pedal “feel.” It’s a driver preference, but getting it to where the driver likes it can result in better lap times.