Do I have to worry about condensation on plywood over rigid foam insulation in the attic?
I am sorry but this sounds like horrible advice.  Rigid or spray foam should not be used in large attics unless you just have money to burn.  For your $ fiberglass blown in insulation is perfect for your installation plus plywood.  (Fiberglass over cellulose since insects may love the coziness of the "wood boxes").  

Also in large attics you ONLY insulate near the top floor ceiling.  Insulating the roofline is useless.