#2 Pressing the backline
Pep's teams have the symbolic comfort in midfield with gifted midfielders who are extremely comfortable with possession and passing the ball around. Manchester City's defenders are decent on the ball, but not on the level of the likes of Pique and Ramos.
This is something that Emery can target by asking the likes of Aubameyang and Mkhitaryan to press both the defenders as well as the goalkeeper as the Citizens will start most attacks from the back.
Jurgen Klopp and Antonio Conte showed the way when they took the game to City even without possession. With the likes of Otamendi not great passers of the ball under pressure, Arsenal should look to win the ball high up the pitch and attack the City goal.
City's midfield is full of creative (low centre of gravity) wizards who can easily pass the ball around even when under pressure, but they aren't strong enough to receive a long ball under pressure.
Unai knows that the likes of Bernardo Silva, Kevin De Bruyne, Leroy Sane, Raheem Sterling and David Silva aren't good enough to play as target men and therefore must force City into playing it long by pressing the back line.