Does it matter if the ball crosses over the sideline in the air before crossing the goal line plane?
The answer, of course, is “it depends.” If the runner is grounded, as long as he crosses the plane inside the pylon the goal line extends, and the ball can be outside the pylon. The plane extends through the sideline. If the runner is airborne, however, the ball has to pass inside (or over) the pylon for the TD. Otherwise, it’s out of bounds where the ball crosses the plane of the sideline.