Is Sakun monotheistic?
Edited to add: on second thought, I think that this is sort of part of what you are asking.
Let's see... if the main anthropological differences are that magic is faith-based, real and widely known to be so; there are no significant monotheistic proselitist groups to speak of; and the two most visible religious groups are called "loving fist" and "stillness"...
Then I would assume that the exact nature of Sakun is highly correlated to its own self-image as contrasted to Aiken. To some extent both faiths will shape themselves in order to emphasize that they are indeed different from each other, particularly in matters that might lend them support and sympathy.
Since I picture Aiken as sort of Unitarian Universalism on magical steroids, with a sort of vague doctrine that is routinely glossed over on behalf of actual practical action with uncomplicated, pragmatical justificiation and a pechant for attempting to appeal for various mindsets at the expense of doctrinary coherence, my tendency is to assume that a complementary faith would spontaneously develop that might offer a place to those who don't fit well into those expectations.
That would be in some senses a highly individualistic, or at least customizable, faith. Since it would have comparable access to faith-based magic, it would be somewhat bolder than in our world, and more given to spectacle. Its lack of interest in proselitism would perhaps be a direct result of its individualistic nature: desire to convert others would be seen as a sign of deep insecurity. It would both value and need a lot of personal initiative and scholarship, because there would not be too much effort from existing members to ease up new converts into the doctrine. And a major part of its activities would be, in fact, bridging up the various forms of the doctrine into mutual understanding and a modicum of common language.
The end result would be a wonder of intellectual ambition, as the vanity and sincere spiritual ambition of some of the finest minds of that culture would hone each other into accomplishments that can endure the toughest of questionings and sustain the proudest of accomplishments. It would be a challenge for insiders to describe and a nightmare for outsiders to understand, but that would be an accepted state of things, to the extent that people only rarely realize that it might have been different.
It would have wondrous art, including music and performance, since those would be among the most effective ways of connecting the sages with the general public. Whole communities would have cultural identities shaped in no small measure by their sympathy and allegiance to specific subvarieties of the faith, connected to specific sages and their lines of spiritual inquiry and expression. There would be therefore many competing doctrines, but for various reasons the desire to understand and effectively communicate with those competitors would be a very frequent, very respected value in most such communities.
Therefore, the contrast with Aiken would carry some measure of snobbish undertones, as the average Sakun adherent would instinctively think of Aiken as a doctrine that does not dare to differentiate itself enough to develop its own potential, that tries far too hard to be all things to all people, ending up as a jack of all trades with diminished accomplishments. There is no way to test that judgement, but it is confortable enough to be readily accepted by someone raised in a Sakun culture.
