" Is silicone caulk at floor joint still recommended for avoiding cracking there? Or is this not needed if using epoxy? "

Caulking AT ALL changes of plane, regardless. Never grout at any change of plane.

Thanks

What is happening here?

I did not even look at the pictures other than the wall floor joint area but as Hallett & Co.. asks, what is that? Grace Ice and Water Barrier is an exterior product. What is its purpose and where else is this used? This has all the looks of a frankensystem, as it appears to be multiple brands of product, with no though to if they should be used together. For sure you will have zero product warranties because of that.

In addition, it looks like the seams are exposed and the nails are not covered I hope this is not the case in the shower area.

Ignore that second photo-

" Ignore that second photo- "

There is only one picture you posted.

The excerpted segment of the photo is showing a part of the (steam) shower wall that had to be re-done; you are seeing-it mid-correction.

Thanks for the input with regard to the flexible silicone caulking at plane changes.