It took me a few years of falling in rivers to figure out that studded boots are superior to those felt only boots. They shouldn't even sell felt only boots.
Like mentioned, wading boots are sized to fit over a neoprene stocking foot. Each company will vary though. I wear a 9 1/2 normal shoe but my Chota boots are size 10. I just added studs this fall for a trip to the Pit River. They are made by Simms and you just screw them into the felt soles. They add way more traction then just felt.