I live in the Northeast area and own a split level home with an attached one car garage. All the walls and the ceiling are open and exposed except for the wall that is attached to the main house. It is covered in drywall. I plan on dropping the ceiling to create storage above the garage, in the peak and I also want to insulate the walls. The final layer of the finished walls will be a plywood product by Georgia Pacific called Plybead. It is basically plywood with a beadboard effect. My question is do I need to put up drywall first (and if so do I need to tape and mud the joints) after insulating or can I just put this plywood product over the studs and insulation???