We really do not know what sort of rulers Ferdinand and Miranda will be, as they are both quite young and naive in the play, and we do not see them in positions of leadership.
Ferdinand seems an honorable young man, willing to work hard to win Miranda. He is quite conventional, following the behavioral and ethical norms of his culture scrupulously. There is no evidence that he would be a bad ruler but no real evidence that he would be a great one, as he does not display any great evidence of intelligence, originality, or leadership skills but seems more a responsible follower than a leader. As he grows older, he may become stronger, but he strikes me as average, likely neither to do great good nor great evil and to be guided by his advisers rather than to be particularly original.
The role of female royalty was normally to produce "an heir and a spare" and not to cause a scandal. Miranda is a pleasant young woman likely to behave with a certain propriety. Her upbringing on the island may be a disadvantage, as she would lack a powerful network of friends, not know much about court intrigue, and lack knowledge of the minutiae of court etiquette, because Prospero, a father focused on his own scientific and philosophical pursuits, would probably not know much about female court culture.