Il est bien de sound very strange to me in both case and in general. So I would go with
il est bon de in both case.
il est bon de is very uncommon. The only sentence I can remember with
il est bon is a song based on a Bible translation from the 1870s...
You would use
C'est bien in modern French. In this regard, the subtle difference is that
c'est bon means it is good to somebody or for something specific, while
c'est bien is good in a more general sens. For example, you would say
C'est bien de trier les déchets
because sorting your wastes is inherently a good thing and this is what you want to stress. However, you would say
C'est bon pour la planète de trier les déchets
if you want to stress that it is good for a specific object, here planet earth.
So to answer your question:
C'est bon de manger des légumes régulièrement
Means that it is good to you, for your health.
C'est bien de manger des légumes régulièrement
Means that it is good in general, for example because it is more ecological than meat, etc...
C'est bon de vous avoir rencontré
Means that you fell good meeting this person. You would say this, for example, if you felt down, met someone and that person cheered you up.
C'est bien de vous avoir rencontré
Means it is a good thing beyond the scope of you two. For example, your meeting will lead to a promising collaboration on a important projects.