If you put a lock on, they may either ask you to take it off before they take it, or they will just cut it off if they feel the need to. Same with zip ties. With laptops, all you have to do is put them in a separate tub and that's it. X-rays won't affect your laptop.
When I travel I refuse to check baggage, more so because of the ridiculous fees that they charge, but also because I don't trust random, near-minimum wage baggage handlers with my stuff. Charlotte's a nice airport (spent 6+ hours there on the way home for Thanksgiving getting drunk for lack of a better thing to do). Safe travels!