If any of the soft white tile is going on the walls and trim is needed (maybe it is? I can't tell from your post), then I would look for a white schluter that matches the white in the tile. I think black or brass will be too much contrast. The tile is really pretty - I think letting it stand on its own with a Schluter that blends in would let both the tile and your other bathroom elements pop more. Just my two cents!

Is the Schluter for the floor or walls? I've never heard of using it for floors?

Cpartist, it's for the transition between tile to hardwood on floor. Yes, this is the appropriate application.