Hi Horukuru,
Henry can add his bit, but the short and simple answer I'd give is this. As you zoom up, the exit pupil of the scope gets smaller, since the exit pupil is always objective diameter divided by magnification. The image begins to become visibly dimmer when the exit pupil becomes smaller than your eye's pupil at the light level you are viewing at. With the ATX 95, at 30x the exit pupil will be just under 3.2mm or a little less than in a 10x32 binocular. At 46x it would be 2mm, and the image will start to look visibly dimmer in all but the most glaring light. At the 72x maximum magnification of the ATX, the exit pupil is down to about 1.32mm which is much smaller than the pupil of your eye at any light level. Your EDG 85 at 60x would have had an 1.42mm exit pupil, likely giving a very slightly brighter view than the Swaro at 72x, but since the Swaro has a little bit better light transmission, the difference would not be very much. Your old Nikon ED 82 on the other hand, has at 75x an exit pupil of 1.1mm, and with slightly lower light transmission on top of that, markedly darker image than the big Swaro at 72.
As to CA, the level of longitudinal CA in the image the scope objective creates is the same for all magnifications, but just like detail in the image gets easier to see with more magnification, so do image defects, so the higher the magnification the better you see the CA that is there. Now, Nikon scopes have less CA than most. In my view only the Kowa 883/884 has less CA than the Nikons, Zeiss about the same and Swarovski models have had a little bit more. So, at equal magnification to the Nikons, the Swarovski could show more CA. Also, since the Swarovski zoom eyepiece has such a wide angle, you will be able to see more lateral CA far off axis than in the Nikons simply because the Nikons with a narrower fov will not show anything as far off axis as the Swaro does.
If your ED 82 and EDG 85 at maximum zoom magnification was not sharp, you have unfortunately likely had scopes that were not quite as good as they could have been. My excellent sample of the ED 82 is sharp (very sharp) up to 75x, but a good sample of the ATX 95 is even sharper at its maximum zoom.
Hope this helps, and enjoy your new scope.
Kimmo