The perfect ruck.
Ball carrier gone to ground ‘posting’ the ball back supported and secured by his forwards.
As a result in pic 2, clean quick ball for the scrum-half.
I think that perfect Ruck is where the ball is secure and accessible, but you do not have many forwards stuck in it. Too many forwards take a vacation in a Ruck.
Absolutely right, you only need the minimum amount of players to secure the ruck. The photo shows it perfectly executed with three players on their feet shielding the ball carrier with a clear access to the ball.