Moldings

A bullnose has one rounded, finished edge. It goes wherever a tiled surface stops in open space: the top of a half tiled wall, the outside corner of a shower curb, the edge of a window return. Without it you see the raw tile body.

For most jobs, three: a bullnose or pencil liner for exposed edges, a base or cove piece where the wall meets the floor, and a chair rail or listello if you want a horizontal break. Count the linear feet of each before ordering.

In the same range and finish, yes. Across ranges expect slight differences in tone, since stone is quarried in lots. Order trim with the field tile in one go so both come from the same batch.

A pencil liner is a thin, rounded strip about half an inch wide, used as a fine edge or divider. A chair rail is wider and shaped, meant as a horizontal band at rail height. Both finish an edge; the chair rail makes more of a statement.

Yes, and for a modern look many people do. A metal profile gives a crisp square edge and costs less to install. Stone moldings match the tile itself, which reads softer and more traditional.