USB and wireless are two seperate kinds of installs. When choosing a printer to print to you must make sure that printer object is tied to the physical connection type you configured it for otherwise the printer will always apear offline.
If you plan to both USB and WiFi print then you will need two seperate objects for both on your Surface. This may or maynot cause conflicts with your scanning applicaitons so tread carefully. When in doubt all you should have to do is configure the printing port to go over WiFi/Network or USB in the Print Properties area.