I had to look up "Acid Free Artcare Backing Board" -- from the name it was not clear that it is a foamcore material. So if one is seeking information, it is better to provide links and/or more background information, rather than less info if one expects others to help out.
The material used for the window and mounting board directly influences what is used for the backing board. My 16x20 8-ply windows with a 4-ply mounting board (8x10 prints) is a rather stiff package that really does not require any backing board to maintain stiffness, though I use foamcore as a backing board for physical protection in the frame. A thinner package -- say 4-ply window and a 2-ply mounting board does need a bit more in terms of a backing board.
I find attaching the print to foamcore with a window over that to be a bit on the cheap side. Foamcore is so easily damaged that it does not come off as a quality permanent presentation. Perhaps fine for art fairs.