You indicated you were going to use a surface waterproofing on the shower walls prior to tiling. You do not want to create a moisture 'sandwich'...IOW, you only want one vapor barrier in the wall. If you use the normal paper faced insulation, slash it after installation to compromise the vapor barrier so you only have one in the wall thickness. As to what Mapai products to use? No experience with them. I know people who have used RedGard and some of the Latticrete products, and I would expect the Mapai products are as good. The key to installation is to get the film thickness at their specified value and make sure you have no voids.