[Illuminated One]

I have the following theories:

Temple checks are before preaching

Friendly checks are before enemy checks


One way to really check it is to make a large map with 2 nations played by you.
Take a province that's very remote so that it's not influence by dominion from other provinces.
Get a nation (A) with a h3 priest give him the sword that makes him h4.
Now you have a priest with 120% preaching chance.
The other nation (B) gets dom 10 -> 100% temple spread chance.
Build a temple and a castle in the remote province with nation B and siege it with nation A.

Then do the following:
Preach it to neutral dom, and then let only the h4 priest preach.
The priest should always +1 the dominion, the temple should have a 100% increase chance if there is neutral dom and a 95% chance if there's enemy dominion.
Ok, now you'd have to host it for a lot of turns and if the province is still neutral the temple spread happened always before the preaching.
If not then the preaching made the province +1 dominion on a turn and the temple failed at the 95% chance check (the good thing is the temple can never take this back as the priest will always procude 1 dom until dominion is 4 so you don't have to check all turns, just the last).