A Co-Narcissist generally is far more affable and compliant than a Narcissist would be. But a Narcissist is a Narcissist is a Narcissist.
Just because someone naturally tends to submission, suffers with pleasure and bows to adverse circumstances without complaint, for example because it often seems much easier and more convenient (at least at first glance), does not automatically make him a better person. The good just like the evil is to be found in pure form rather rarely. Except maybe psychopaths and angels. Otherwise, here again as almost always in real life the old rule applies:
The dose makes the poison.
The Ideal World Syndrome
The Narcissus and his Co-Narcissist fit together so marvelous, because they complement each other (almost) perfectly: the Narcissist is hungry for attention, appreciation, care, unconditional submission and constant confirmation of his self-esteem and this all should happen as harmoniously as possible. Otherwise he feels miserable, small and inferior. And if the Narcissist suffers, who is to blame for it? The Co-Narcissist! If he or she does not find someone else to blame for it.
The Co-Narcissist, too, loves harmony. He hates conflicts and therefor subordinates himself unconditionally. He does everything to make sure his Narcissist is doing fine. Even if that meant that he delivers himself completely to the needs of the Narcissist and does without the satisfaction of his own. This is not that easy as one might think. It usually does not quite work out with the unconditional submission. Because the Co-Narcissist is also thirsty for attention, recognition, care and constant confirmation of its self-worth, secretly. Otherwise he feels miserable, small and inferior. And if the secret suffers, who is to blame for it? The Narcissist, of course! That's why those relationships usually are dysfunctional over a longer period.