I'm interested to know why you guys would pack out the recess? Everything I read said cut edges everywhere and never butt up tiles, is this the one exception that proves the rule? was gonna do the recess in metro too but I'm starting to think mosaics (I know how predictable!) might look ok...
Simply just to remove the two thin cuts you took out of the bottom row of tiles. They won't be butted up, I imagine you'll be putting a trim around it to tidy up the edge?
Dunno ref Mosaics inside the niche mate, personal choice so do what you fancy. I would tile the insides of the niche in Metro, and just the back of the box in Mosaic. That way if you don't like it, you can easily metro over the top of the Mosaics in the back and it will be fine......?