I really think you'll have to try 'em on first. Some companies size the boots so ... lets say a size 8 will buy the 8's and the thicker neoprone bootie has been factored in.

I just bought boots and I were a size 9 ... I bought size 9 and they fit even with the thick neoprene feet on my waders. Other makers size as normal, so you have to size up to get the proper fit.

IMHO, you should buy the boots as if you were going to wear neoprene foot waders then wear a thick wool or neoprene sock while wet wading. Or buy two pairs

Oh, ... Welcome to the forum!!!