I am renovating my bathroom. Replacing a vanity in a 40.5 inch opening with walls on either side and in the back. Would like to tile a backsplash around the top of the vanity. I've been looking at vanities 40 inches wide and smaller. What size should I select if I want the tile to extend down the side of the vanity a little ways? How much clearance do I need to install the tile? What if there is still a little space between the tile backsplash and the vanity...would I just caulk it? Novice renovator here!