Question about bolt carrier

Just to confirm: I assume the bolt carrier for the 6.8 is the same as that for the 5.56, right?

Second question: I have seen two distinctly different carriers. One carrier extends back to almost surround the firing pin entirely, so that when the carrier starts its rearward travel the firing pin is pushing back only briefly on the hammer before the carrier takes over that job. With the other that part of the carrier is much shorter so that for most of the carrier's movement rearward it's the firing pin pushing back on the hammer. In other words, with the carrier group out of the gun, the latter one lets you see the rear-most cm of firing pin but with the former you can only see the last couple mm.

The first one is on a late model Stag 5.56 and the latter is on a 2004 vintage M1S 6.8. The Stag's seems much nicer so I wondered: Is this is an update?