Wow, so many questions.
The optical upgrade from the original 5-42X56 to the Gen II has to do with improving the IQ when the scope is near the limits of adjustments. From the official website "The image quality has also been further refined especially near the maximum elevation amount."
The Gen II has the shuriken turrets with the locks, except for the model with the writable turrets. The writable turrets are no lockable.
As I have said many times before, I am an F-class shooter and far too old to shoot PRS properly. I have very little experience with the 5-42X56 (the original), but I did shoot the Gen II with the FML-WBR reticle and the writable turrets. I had zero problems getting behind the Gen II, at any magnification, even though it was not my rifle. I thought the reticle was elegant and conducive to high precision as far as an FFP design can be precise (boo, hiss, get outta here you bum.) My current F-class riflescope is the incomparable March Majesta, which I have set at 80X using the MTR-WFD reticle. (To give you a frame of reference.) The field of view of the Gen II was, in a word, AWESOME. I shot mainly at 100 yards to get the zero, but I did scan the rest of the range to get an impression of the DOF and FOV. I was running it at around 30X and didn't need to mess with the side focus. I did crank up to 42X for the zero at 100, and did have to touch up the side focus. Easy peasy. I then put it back to where it was set, using the writing on the turret as a guide.
The March riflescope are legendary in how they do not flare when tracking close to the Sun. I can tell you stories of late afternoon/early evening matches in Lodi, which faces west. I had to cover my head with a towel, but I could see through my March just fine.
I did not get to verify the mirage performance with the Gen 2, but I am very familiar with that performance with the March-X 10-60X56 HM (which I used for years in F-Class, always set at 50X regardless of mirage), and for the last 18 months with my Majesta always set at 80X for the 1000-yard F-class game.
