Measure the length of the wall to receive mirrors. Then based on the width of each mirror panel, determine how many mirror panels you will need.
Let the mirror company install your mirrors. Wall mirrors for a studio will be large, typically 72 inches by 100 inches. They are extremely heavy, and if they are broken during installation by the mirror company, they will be replaced. But if you broke one, you would have to replace it yourself.
Direct the mirror installation crew to center the row of mirrors as best they can across the room, so the amount of wall showing on either side is nearly equal.
Order your mirrors to have an outer beveled edge if you want the mirrors to appear to be framed. Don't have the edges beveled that will be side-by-side in the center of the mirror. Make sure only those edges that will form the bottom, top and the far outer sides have bevels.