I can't answer questions about specific waterproofing, as each situation is unique. I can tell you a wet room such as this shares waterproofing with the walls, shower floor, and the skirt of the tub. Correct waterproofing is critical for longevity and functionality of wet areas. I would suggest having a professional provide details for your situation.

We do fiberglass for the shower pan upand g up the wall several inches so that no matter what it won't leak. Smells really bad for a few days though. Then the rest of the backing is as per usual. Shower pans and techniques form Home Depot just are not reliable in the long run.

Use the Kerdi waterproofing system.

Schluter/Kerdi is available through the Home Depot.