My experience is its good for people playing perfects to either read the sheets first, or already have some basic Cathar knowledge. They are the IC experts, and really the only people making fully doctrinely informed choices. So for players who like transparency on their own characters, it’s good to know fairly early on.

For everyone else it matters much less. Frankly most folks were not experts on religion and their beliefs are based more on community and authority and localization than on formal doctrine.

So, like Pierre doesn’t really need to know about the dualistic philosophy of the demiurge. He needs to know that those fuckers following that foreign asshole and the asshat king of shitty France murdered his family and fuck them and their fucking demands.

… But then, I’ve been told that playing the game with me goes differently in that I’m all realpolitik about religion. So, YMMV. 

Also, I have played it once or twice where I was the only main character perfect, and we just dealt with it by people asking questions IC, and me answering IC about how my character interpreted doctrine. It shifts things around, putting a lot of emphasis on how we build meaning together instead of how we jointly interpret independent external knowledge.