Polished, matte brushed or bead blasted? Your rifle, your choice, its just about appearance.
For a crown, either a shallow angle like 11 degrees (or 10, 12, whatever, it isn't going to make any difference), or 90 degrees stepped and recessed. Either sets the crown into the barrel a bit to protect it, either works.
If your 'smith is experienced in making BR rifles, he will have a preference. Why not just ask him?