Hi Keith, did you end up installing before or after the tile? I am now wondering the same for my bathroom.

Mount the grab bars on top of the tile. Placing tile around the ends just won't look right and will create more areas for possible leaks.

I think mind blend in nicely and are so functional when I am getting in and out of the shower.

This is the end of my shower by the shower door where I would enter

The niche is at the opposite end and has a bench and this horizontal grab bar would theoretically would be available to grab if I wanted additional stability wandering around the shower or rising from the bench. You do want to consider orientation in terms of horizontal, vertical or at a diagonal.

I have two hand held showers so that I can easily access a hand held shower when I was sitting on the bench. This is a great feature as I don't have to deal with attempting to control a hose from a distance or go back and forth to put it back in the holder.