If you have good quality data and are refining atomic displacement parameters, you need to go to high angle (like >130) to be able to distinguish the different effects on the intensity.
Depending on which material and unit cell, you could get away with a single peak, but probably not the best,
For QPA, you need to go high enough angle that the cumulative intensity increase with angle is constant (normally 70-90 °2Th.
In general, you want to collect as much data as possible. I discuss this in terms of QPA here: https://doi.org/10.1107/S160057672100371X