I'm going to avoid the physics and chemistry lessons concerning cooking meat. Just know that heat absorption by the meat slows as the meat temp rises closer to the chamber temp.
Use a smoker temp initially that maximizes good smoke on your pellet smoker at the start (180°F/200°F/225°F). As the meat reaches the stall (140‐165°F meat temp) in 3-4 hours, crank the smoker temp up to increase the chamber temp-meat temp difference. 275°F/300°F/325°F/350°F/ and higher, I've used them all. Higher temp = faster clock. The difference in texture and tenderness is negligible. Wrap/don't wrap, it's up to you. No wrap = crispy bark. Foil wrap = soft bark. BP wrap is in the middle.
Fat does add to juiciness of the meat, but melted collagen in the hard-working muscle is what actually makes the meat tender and juicy. Butts aren't lazy steak muscles. An undercooked butt is dry and chewy. An overcooked butt falls apart but is still tender and juicy.
If resting the butt in an oven or cooler, wrap it.
This is solid, no-nonsense advice. Thank you, sir!