Keep in mind that great sharpness will easily out perform over more magnification with less sharpness.
It's hard to find specs anywhere but some manufacturers produce optics that exceed what the human eye can resolve. You'll find that in top glass, like Swarovski, Leica, Zeiss and high end Kowa. If price is an issue, I would wait save up for better glass than buy something border line that's affordable today.
Whatever you decide, go with the best resolution so you can spot the subtle details like mirage and don't fall into the trap of cheap high magnification glass expecting to see more, because you wont.
As for bino vs spotting scope, consider eye strain over long exposures. With binoculars, both eyes are in the game and will stay in sync, but with a spotting scope, the eye you are viewing with will strain more than the other eye, then you'll be funky until things normalize.
A spotting scope is fine for brief use, but if you want to stay on it for a long time, the binos can be easier on your eyes. Also with a spotting scope you can get high magnification at levels that are not available in binoculars. So if you just really want to zoom, you might have to accept the eye strain after extended use with a spotting scope.
As for the ideal magnification (assuming you're a PRS shooter) I would try and stay as close as possible to the magnification you use on your rifle scope. That way while you are spotting, you'll be internalizing what you see to impacts in the same way it will look when you're shooting. That way you will be in tune with what you see in the same way between both optics.