here are some optical basics to think about.
The exit pupil of a rifle scope (any optical telescope) is the diameter of the light bundle where it enters your eye assuming your eye is at the optimum separation from the eyepiece. It is not a place where an image is formed. Images in a rifle scope exist only at the target, the first focal plane, the second focal plane, and on the retina of your eye.
If the diameter of the scopes exit pupil is larger than the iris of your eye the light which does not go through your iris ls lost and does not add to image brightness.
The diameter of a scope's exit pupil cannot be larger than the objective diameter divided by the magnification If the scopes exit pupil is smaller than the eye's iris the brightness of the image will be the area of you're eye's pupil divided by the area of the scopes exit pupil. That number is purely from the spreading of the light. It does not include any reflection or absorption losses in the optical components.
So the optimum magnification for a given objective size for the brightest image is to have the objective size divided by the magnification to be exactly the size of you're eye's fully open iris which is typically about 6mm for midlife humans. As humans get older the irises of their eyes get stiffer and don't open as large. For example, a 50 mm lens at 10x would fill a 5mm iris. That's why 3-9x50's have been popular for many years. A larger objective will not give a brighter image at that magnification. With any scope where the maximum magnification exit pupil just fills the iris the apparent image brightness will remain the same over it's range of magnification adjustment.
Image brightness isn't the only important factor to being able to see well in low light. When the human eye becomes dark adapted it loses color vision. That's because the eye has two separate kinds of sensor called rods and cones. Cones are color sensitive but they don't dark adapt. Rods have the ability to increase their sensitivity by about a factor of 1000 over the light level where the cones cease detection.
Rods and cones are not uniformly distributed over the retina In the fovea (the center of vision) there are lots of cones and only about 1% rods. Over the rest of the retina there is a higher density of rods than cones. The result is that the resolution of the dark adapted eye drops by about a factor of ten. Just above the limit of color detection you can resolve image with a 10 times better linear resolution than just below where color vision stops. So it takes a 10x scope just to restore the >resolution< of the unaided eye. No scope can make an image's surface brighter than it would appear with the naked eye. To do so would violate laws of physics. It really becomes impractical to put a scope with a large enough objective and enough magnification do much more than just restore your naked eye capability once light is dim enough for color vision to cease and the rods start to become dark adapted. To do that requires electronic devices like image intensifiers , integrating video cameras, or artificial lighting.
Today all but very junky scopes have decent coatings on all lens surfaces. Each air-glass surface without coatings will reflect about 4% of the light. Modern scopes can get the total loss down to below 10% light loss. When you look at the lens of a scope with illumination from behind your head the less reflection you see the better. Ideally you would see no reflection.
It's difficult to make coatings which stop reflections over all visible wavelengths. Dropping reflections from 10% total to 5% total is not nearly as important as dropping them from 20% to 10%. Don't expect any leaps in performance in optical scopes. The better brands are close to theoretical performance already.
The whole point is don't knock yourself out trying to find something which doesn't exist. If you need a scope which will allow good resolution beyond civil twilight (sun more than 6 degrees below the horizon) the practical choices are spotlights, IR illuminated image converters, image intensifiers, and perhaps thermal scopes. Any of those may be regulated by hunting laws, including hunting at all after sunset.
For more information on optical design and how it relates to the human eye I recommend this old (1962) military manual:
opti 502 syllabus
It's big but it's free to download. The manual is in .pdf format.