Screws for pyrex display shelf

Hi. I'm putting up a pyrex display shelf in my kitchen with handforged iron brackets and a 2" x 12" x 106" shelf, but I don't know whether I should request the countersunk head drive screws that usually come with the brackets, or if I should get the heavy duty lag screws that are also offered. The screws are not interchangeable, so I have to decide before ordering. Any help would be greatly appreciated.