Aha, so I didn't understand it correctly before. In what way will it scale based on the number of converted followers? IIRC, it will be the first belief where the benefits will scale based on the number of conversions?
Will the Way of the pilgrim remain the same (since it allows for unlimited missionary spamming to nearby foreign cities)?
Yes.
Apostolic (right now in testing) is 25 Food/GAP per spread, scaling with # of conversions (so if you convert 1 it becomes 50, 2 75, etc.).
Way of the Pilgrim is 15, scaling based on the number of followers of other religions in the city (so diminishing returns for hitting the same city over and over).
G