Hi Sandra! Welcome to the forum, and the world of smoking!
As for the picnic, if you want to slice it, an internal temp of no greater than 180* should suffice. If you wish to pull the meat off the roast (pulled pork), you will need to take it to 200-205* internal temp.
In either case, low and slow is the key to a good product. 225* cooking chamber temp is the norm, as this will create a very tender meat, from what is a lesser cut.
To get a crunchy skin or crust, you may opt to spray with a fruit juice such as apple, or mop with a baste/glaze containing some brown sugar. The sugars will caramelize and harden as the cooking progresses. The application of sugars should not be used until later in the cooking process with larger cuts requiring long cooking time, as they will eventually burn/scorch, so I do this after the internal temperature reaches at least 160*, if I slice, and 175* if I pull the meat.
Also, when the desire internal temp is reached, wrapping in foil or placing in a cover pan and resting a couple of hours while wrapped in towels will redistribute the meat's juices in the roast.
As for smoke, mesquite is good with the heavier flavors of the picnic. I've used hickory as well, but with a shorter smoke time, as it's a sharper flavor. Milder smoke woods like cherry and apple are very good also.
I generally remove the smoke wood when the internal temp reaches 160* with large cuts of meat as with the picnic.
Eric