I open carry in PA often (at least once a month).
AFAIK, there is no specific requirement as to the type of holster that would be acceptable for legal open carry. As long as the firearm is securely held and protects the trigger guard, I would say you are fine.
However, having said that, a thigh rig might attract more attention than a pancake rig.
On your other question, you are correct. The PA permit is a "License To Carry Firearms" not a concealed carry permit. However, on-foot open carry is legal in PA (except the city of Philly) without a permit. With the permit, you can open carry in Philly and in your car.