Maybe I've missed some info along the way but how do the NV devices do at high magnifications? A lot of what I read is about what can be seen at 1x or 3x.
They can do very well.
If the device has a C-mount objective lens (like the Mod 3c), you thread the objective off and replace it with a nose piece. Then it goes directly into the focuser like a 27mm eyepiece. It can be barlowed like a regular eyepiece. One can also use a focal reducer.
If the device does not have a C-mount objective (like the PVS-14), you get the Tele Vue/TNVC afocal adapter. In simple (if not elegant) terms, it clamps on to the end of the eyepiece. If the host eyepiece has a shorter focal length than the NV device, it acts like a barlow. If the host eyepiece has a longer focal length than the NV device, it acts like a focal reducer.
Emmission nebula are very sensitive to speed. But even at Maksutov focal ratios, it has much greater sensitivity than your retina. Yes, you can see the HorseHead nebula with a 90mm Maksutov. The slow speed and aggressive line filter make it a grainy view though. It's just one of those things that is fun to do just because you can. In actual practice f/13.8 on nebula is not where you want to be. I found my f/9 Newtonian perfectly enjoyable though.
Stellar objects (i.e., clusters) and high brightness objects (some PN's and galaxies) are much less bothered by slower speed. In that same Maksutov, the NV eyepiece operating at 27mm thoroughly trounces a 22 Panoptic on open clusters.
NV users due tend to get on a speed quest, directly analogous the aperture quest conventional observers suffer from. So let me say this: The comparison is not the F/3 wonder mirror you don't own (yet ), but rather the comparison with the NV eyepiece to your standard one.