#1 on the first question ; yes that is the reason to patteren the gun. to see where your patteren is hitting.some guns my hit high or low.you can get adjustiable sights so you can move the point of impact.

#2 it is best to get several different shells and see which puts the most pellets in the kill zone. it cost a little to get all the different shells,but it will be worth it in the long run.

I am not a hunter I am a whitetail population reduction specialest

remember keep your back to the sun, your knife sharp, and your powder dry.