Yes, dry apple is excellent for smoking. I am in BBQ country and a bit of an enthusiast. I use apple, cherry, and hickory though grape vine is nice and for a stick burner white oak is great. Apple has a fairly mild and sweet flavor that works great for meat that has little flavor like chicken breast, pork loin or butt, and fish.
For bbq, you don't need the wood to be bone dry but it doesn't hurt anything either, but you do want it dry. If you were using a grill to smoke, you'd probably want a bit more moisture but in reality, for bbq the moisture level is not critical. Maybe for stick burners it's different but I use Weber bullets and they are fueled by charcoal and flavored by wood.