Please please please don't sweat smoking a pork shoulder roast. You can cook/smoke them at any chamber temp between 225F to 375F, so use the cooking/smoking temp you are comfortable using. The only thing that changes with temp is the time to finish.
Use meat temp and time as a guideline for when to probe for tenderness. An underdone shoulder will taste dry and tough. An overcooked shoulder, which is actually kind of hard to do if at 250-275F chamber temp if not wrapped, will be soft, juicy, and mushy, but definitely tasty and edible.
Relax. Your eyes and brain are not microwave transmitters, so you can't watch or think it done. Let it do its thing in the heat and check for tenderness toward the end of the cook.
Pork shoulders are easy and forgivable. The vast majority of folks who roast their first one take them off too soon, get tough and dry meat, and believe it was overcooked. Take their lesson to heart and be patient.
Enjoy your pulled pork...and definitely use a finishing sauce!