My leeds fan mate is convinced that Harrison is a really good winger. Personally this is my take on him. He's not good enough to make Everton better.
I feel he is the type of player who has good stats over the last 3 seasons or so because of how Leeds play. Leeds would often bomb the full backs on and this would open space for Harrison regularly and with the multiple chances he would get he would be very inconsistent.
I think he's an OK player, but if he played for a team who play a more conventional style, his numbers would go down significantly. I don't think he improves Everton, possibly good enough as a rotation option with what we have now, but we need ready made players to improve our team in the attacking positions. I would much sooner go for Harvey Barnes from Leicester. So Harrison .... not for me.