I have written this many many times over the years. I am an absolute believer in a 3x9 scope. You get a fairly wide field of view at the lower scope settings and on 9 power you have enough magnification to see a coyote at 223 ranges. Besides that, the 3x9 is probaly the best bang for your buck due to the popularity of 3x9 scopes in general.
The 50mm lens should suck in enough light for any calling ssituation.
I am even more set on my belief that an AO does not belong on a coyote calling rifle, especially for a new caller. You just don't need the hassle of an AO scope. Disclaimer: There are some big country calling situations where more power is needed and an AO can be used effectively. I can assure you of this, you will not miss a coyote due to the parralax adjustment on a non-AO scope, you very likely will miss at least one that is directly attributed to an AO.