Harland is a Van Nistelrooy clone.He won't eclipse Mbappe not by a long chalk. It would be a similar battle of when Messi and Ronaldo were at their peaks and neither will come close to matching either of their achievements. Although both would give it a good go.
Mbappe is an Henry clone.
Neither will be Messi nor Ronaldo.
Mbappe is the better footballer; Harland is the better goalscorer.