Part of the concept of Terrae Vertebrae was the split between Elven and Dwarven influence on human cultures. This was part of the concept: the Pantheistic Elves and Shamanistic Dwarves spawning differing interpretations of human faith.
The Faith was revealed by the Sybil of the Rocks to her Fourteen Scribes. The names of the Sybil, the Rocks and many of the scribes have now been lost.
Any discrepancies in Holy Scripture are down to the fact that the Fourteen Scribes must have used different forms of shorthand. Pointing out that this was silly will not impress anyone, let alone a Questor.
The Napeshene Collegiate Manifest Rite (MR) Emphasis on Differences of the Eightfold God. Complex ceremonies. More Polytheistic. Sited in the Estates Immaculate, at Napesh.
The Cadencian Collegiate Unified Rite (UR) Emphasis on Unity of the Eightfold God, fewer trimmings and trappings. Touch of Pantheism and other universal creeds. Sited in the Novopolis at Cadencia.
The two rites split three odd centuries ago; a split more reminiscent of the divide between Catholic and Orthodox than Catholic and Protestant. The Manifest Rite is the elder. Though not entirely amicable, but the peace is kept. Popular demonstrations, skirmishes – but few wars of Faith and no Mass Crusades. Wars between nations of different rites yes; Holy Wars - no.
The split was over principally a theological issue: no central complaints about (for instance) the use of indulgences or misuses of Church funds and lands (Or rather, only as ancillary mudslinging). The structure of the Church was judged to be more-or-less acceptable in its current state by the UR – though some stream-lining and renegotiation of local/Collegiate relations occurred. The MR does have perhaps the more ‘pragmatic’ mindset of the two, or has more options open for ‘pragmatists’, but is not as such corrupt (or at least, no more so than any organisation that accrues money, power and influence for its own ends – no matter how good those ends are).
Who is in the College of the Rite? Academics. Visionaries. Supreme Grand Masters of Religious orders. Cardinals from different nations. Representatives from international monastic orders. Representatives from national synods. Holy hermits. Questors.
...this is all complicated by the use of deputies, proxies &c. by those too busy/locally concerned to attend.
...plus support staff, functionaries, Clerks, guards, architects, musicians &c. Lots of Legates to be sent out with Encyclicals, &c.
The Head of a College is primus inter pares rather than a supreme authority. Not that they are devoid of power, or that they don't take a leadership role.
Churches: MR where Christian choir and altar would be, stylised house/ version of house [One period of design might have individual small icons or booths; another a large model house, Cathedrals can have a literal house inside them!] for rites. Before this, pulpit & pews. Around it, processional and smaller shrines UR similar but with altar/pedestal (can completely process around), image of the United Eight.
Acts of Faith: Reading the Scriptures. Listening to Sermons. Obeying both. Fasting and other acts of discipline. Regular worship. Crafting icons and other items of religious use. Observing Holy Feasts. Acknowledging and giving prayer to the Aspect of the Divine of that time and place. Communion is taken, for reasons of ‘Unification of the Eight and Man’. On high occasions (and for high persons) it is taken in Eight Kinds: Water, Meat, Bread, Milk, Turf, Vegetation, Wine and Fish.
MR Vestments: Full Catholic medieval grandeur. Variations with region. UR Vestments: Ranges from Geneva gowns to High Anglican.
MR Monasticism: Yes please. Contemplative, mendicant, all the range. UR Monasticism: Yes please as before – but stricter line of division between the regular and secular clergy. “You joined X; stick with X”
MR Hierarchy: Towering, complex. Reaches up to the Collegiate, out into region specific branches, takes in knightly orders, guilds, lay brotherhoods.... Hierarchy goes up to Cardinal level in nations. Cardinals and Synods appoint some members of the College of the Faith; the College has its own representatives who look out for promising talent and can uplift some individuals without consulting the local Synod.
UR Hierarchy: Goes up to the Cadencian College; slightly more emphasis on consensus as result of break-away. Diocese level regional synods with Parish Elders, but beyond that as MR.
Female Priests Unlike Medieval Europe, these exist; given that the Eightfold God has specifically feminine attributes, how else could it be? That said, like Medieval Europe, they are hardly the rule. Most places of worship will have not only a Priest, but a Shrinekeeper - generally a female role. Female monasticism is common and an Abbess is a personage of importance. Women are allowed into the Colleges of the Two Rites, thanks to the example of St Ysodor.
A few notes on play: The 52 Pages refers to Clerics as Prophets - the logic for which may be found here - so any given Prophet may have any kind of relationship with the Church. The logic given in the system extends into the setting: don't expect any given parish priest to be able to perform miracles of healing. They are too busy saving souls.