Personally I carry an external frame pack made for me by my brother years ago. It was originally just a day bag, but lately I mounted it to my homemade frame. I hunted for years (rifle and bow) with an internal frame pack, but hunting in the warm weather (early seasons in this area) I find the internal frames make me sweat way too much. My external frame has high ventilation webbing as the only thing touching my back.

My back feels way cooler now. If I do sweat, it can now evaporate, and another benefit of an external frame, is odd shaped items don’t stick me in the back any more.