Hand-off agressiveness and ruck success

Does ruck agressiveness(team and individual) help to win the rucks?
It is written in description that it increases strength: what strength: of the ruck, of the scrum or just player's attribute "strength"?
It helps win rucks but also can lead to penalties. It is ruck strength.
Black monks, fouls in the ruck or any fouls?
Ruck aggressiveness can cause fouls by you or your opponent depending on setting. Handoff can cause penalties when carrying the ball, scrum aggression penalties in scrums, rhythm overall penalties and exhaustion