There will be swarms of very small, quiet “spy drones” whose mission is to identify targets and light them with lasers. The larger stand off weapons platform drones will then take them out with guided munitions or long-range direct shots. A smaller number of very large drones could carry sizeable missiles for destruction of larger targets.
Given a sufficient stream of munitions, a network of two or three very large drone weapons platforms with 20 mid-size direct fire drones, all supporting about two or three hundred spy drones could conceivably exterminate all humans in a 20 square mile area in a day.
Which seems, increasingly, to be the whole point of this particular line of research.