Every religion, once fully codified, has a founder belief, a worship belief (building), a follower belief, and an enhancer belief. The text of Dharma says "Receive the Follower Beliefs of all religions that have at least one follower in a city, not just the majority religion."
These are all the follower beliefs (from the wiki):
Choral Music: Shrines and Temples provide
Culture equal to their intrinsic
Faith output.
Divine Inspiration: All world wonders provide +4
Faith.
Feed the World: Shrines and Temples provide
Food equal to their intrinsic
Faith output.
Jesuit Education: May purchase Campus and Theater Square district buildings with
Faith.
Religious Community: Shrines and Temples each provide +1

Housing.
Reliquaries:

Relics have triple yield of both
Faith and
Tourism.
Warrior Monks: Allows spending
Faith to train Warrior Monks, medieval land combat units with a unique promotion tree. May only be purchased in a city with a Temple in its Holy Site.
Work Ethic: +1%
Production for each follower.
Zen Meditation: +1

Amenity in cities with 2 specialty districts.
Some of these would combo well- especially the culture/food/housing from shrines and temples. +6 food, +6 culture, +2 housing from every holy site? Uh, yes please!
Work ethic is not so useful for Dharma because it's only +1% per follower of that religion specifically; it's an amazing belief for big cities, but to maximize it you usually have to use inquisitors on your populace, which wipes out the other stuff.
The main issue is that you can't really control what the AI picks and how it spreads, so most likely, you will just end up with warrior monks. You don't get the founder belief, and any city with majority religion can get the building - but you can only have one anyways- and some enhancer beliefs are just inherent to the religion (scripture, holy order, monastic isolation, religious colonization) but I'm unsure about burial grounds, and Crusade/DotF. I'm inclined to believe that's a founder only power. Does anyone know differently?
Dharma would be a lot better if it included "You also get the founder belief of any religion which is followed by at least one city in your empire" so there was a bit of a push towards having a heterogeneous religious landscape. Anyone playing RV will wipe out all other faiths anyways, so it's more of a nice to have.