If we look at the settled population of Pavis County and Sun County together, we see that the six largest cults are:
Ernalda, with 5325 initiates
Yelmalio, with 4950 initiates
Orlanth, with 4700 initiates
Grain Goddess, with 4000 initiates
Zola Fel, with 3500 initiates
Pavis, with 1000 initiates
To me this explains how Sun Dome County manages to maintain its autonomy – the Yelmalio cult is far too powerful for the Orlanth cult to subdue, and so the Orlanthi don’t even try. Instead, cult competition is ritualized in contests and the cults maintain a respectful mutual neutrality.
In Sun County, the Grain Goddess has likely maintained an independent existence (unlike in Sartar where it is subsumed into the Ernalda cult), but it is still under the influence of the Ernalda cult. Contests such as the Garhound Harvest Queen festival provide a way for the main cults to establish their mutual relationship and status.