You don't have to foil a pork butt if you do not wish to. The shoulder is so heavily marbled with fat it will not dry out.
In face I have cooked briskets and ribs and chuck roasts without wrapping with very good results.
Like HOS mentioned watch your temps and use a toothpick for the final test.
When that toothpick goes in like butter and pulls out clean, remove it and let it rest lightly wrapped in foil or parchment paper.
Need those juices to redistribute.
Also, you will be fine using a pellet grill because you do not get a heavy smoke profile like other smokers.
If using charcoal and or wood I would wrap to help them to not get over-smoked.
You will be fine