McGinnis is strongest in a defensive position. Her abilities allow her to dig her heels into any valuable space across the map, and force opponents to burn resources dislodging her from it. During the early lane phase, her heals and large ammo let her outlast most opponents and stabilize easily.
McGinnis greatest weakness is her lack of a "get out of jail" ability. If enemies commit hard, and she fails to fend them off or run away, she often becomes free pickings for a kill. Because of this, it is important McGinnis position cautiously and always have a plan of escape if things go south.
McGinnis has two primary niches. (1) is Babysitting a singular lane and constantly wasting enemy's time by forcing them to come deny her split-pushes. (2) is acting as the backline of a teamfight, providing constant peel, splash and heal to her aggressive teammates. Ideal McGinnis play involves fluidly switching between these niches across match time.