Here's the deal--
* Pretravel and overtravel increase reliability. What do you think stops overtravel? Some sort of screw adjustment or physical block. What happens when the trigger CANNOT move far enough to the rear to release the sear, due to debris on that physical block? The FCG will not drop the hammer. BAD. Repeat for pretravel.
* I have tried the JP, JP modular, and the McCormick modular/drop-in triggers. All have some creep/roll. That said, the JP's can be adjusted to be light, reliable, and smooth, but there is still some trigger movement that corresponds to sear movement. We're talking about roll/movement similar to a 1911, so less than 0.1" of movement (probably less). Reset distance on these triggers is very short, and there is no trigger bounce.
* A good two stage trigger like the RRA NM or WOA will have an extremely crisp second stage. The reset distance is longer. There is some trigger bounce.