Our designer wants to use a 45 degree grout application instead of a finished trim on the edge of glass mosaic tile. Someone at Home Depot told me it could break apart eventually. A strip has already been installed on the left edge of a tub/shower wall and looks messy. The strip on the right side butts up against a door. The design calls for the same angled grout and accent tile border around two different mirrors? Any opinions on this technique, should I get Schluter, or try to find a pencil tile? I found a skinny piece of wood trim that could be painted to cover the edge. I don't know what else to do. This mosaic comes down one side, across the floor in front of the tub, and up the other side.

Also, you can see a bit of a niche in the background. It s not finished because the installers put it up forgetting we had no bullnose. I had wanted Schluter but all the tile is in place except where bullnose was supposed to go. Can a line be cut behind the surrounding tile to slide Schluter in or is that too risky.?The only solution I could find was to buy white 2x6 bullnose from which thy can cut skinny edge pieces but that will be delicate and tricky and may look bad even if they cut evenly.