RE: do ailerons provide lift?
In a turn, elevator is used to maintain the altitude. The bank is what turns the airplane. If you use no elevator, the airplane will turn, but also descend. The more bank, the tighter the turn, and the steeper the descent. That's it.
For a thorough discussion on how airplanes fly from a practical, pilot's perspective, please see the book, "Stick and Rudder" by Wolfgang Langeweische. An aviation classic that makes things eminently clear. The principles hold for models in addition to full-size aircraft.