1) Have any of you used either one of these products in lieu of a regular shower membrane?

2) Is there any real advantage to a bench made of cinder blocks vs lumber. Any construction tips for either?

This is a great forum. Thanks in advance for all your replies.

RedGard is a vapor barrier.

So based on your listing, all that you listed could serve you well for moisture management, both only the RedGard for vapor management.

1) Over the years I've used RedGard, Hydroban, and 9235 in "regular" showers. But not in a steam shower. In steam showers I use Kerdi. There are other products that perform the same function. Kerdi is my personal preference in steam showers.

2) Cinder blocks are impervious to water damage. If wood gets wet, it can swell. No big deal there though, as neither should never see water or vapor, especially with today's membranes. If using cinder blocks or similar, I build on the subfloor and butt the mud slope to the blocks. If building with wood, use kiln dried wood to avoid the shrinkage you'd get from green wood as the green lumber dries out. Wood construction would be built on the subfloor too. Wood framing, then a skin of plywood (if needed), a skin of cement board, then the membrane.