RE: Shooting practice question
I practice from as many of the positions as I can. Changing your posture has an effect on your draw lenght and sometimes your anchor point/sight alignment.
Since I hunt Elk I find it very important to practice shooting from the kneeling (1 0r 2) on my knees and kneeling sitting on my heels. Even this slight difference has an effect on point of impact.
Perfect practice makes for more effective and effortless execution.