Heresy and you!

Prof. Misclick

The church is a mortal instrument that is recognized by secular powers as being the True Faith and is seeking to gain influence, power, wealth, and status.

Deities need worshippers so unless a "church's" dogma runs contrary to the deity's portfolio they will accept worshippers and faithful in all forms, without being overly concerned with which ritual, which sermon, which name, or historical interpretations is taught. Those are all mortal concerns.
Official Clergy are recognized as agents of the church, empowered by the church to speak for it, represent it, and are charged with increasing the church's influence, power, wealth, and status. It is entirely possible that some of the official clergy do not have levels in the Cleric class.

To be a Cleric, divine power is granted from the deity not the church

"Heresy" is against the orthodox church of a deity and not necessarily contrary to the deity itself so as long as they are representing the deity by promoting the deity's portfolio and doing so in recognition of the deity, then they keep their powers.
A Cleric can be part of a heresy but until that heresy becomes dominent, they cannot be Offical Clergy.

* As long as the heresy does not run contrary to the deity's concerns they would not get cut off from their powers.

With the deities being distant it stands to reason that warnings, feelings, messengers from the deity do not exist. Spell failure happens when a cleric strays and clearly damages the deity's concerns. However the deity will give the cleric every chance to self correct since an imperfect worshipper promoting the deity is better than no worshiper. Different deities will have different threshholds.

Official Clergy

Does the deity have a church in the setting?

They can join the Church and get relative NPC backing of said church.

They don't have a church?

They cannot be official clergy without first finding a way to bring the church into the setting (Note that the very act of earning the church in the setting will likely mean that character is Official Clergy of it)

Official Clergy are exempt from laws involving otherworldly entities and necromancy by Gondegal's decree.

The "One Step" rule for clerics still applies.

Specific Rules for Clerics and Heresy

Clerics must select a deity at creation and must pick from the regular domains.
Clerics can earn the perk of customizing their domains by being awesome IG and Bringing the Fun :trade_mark: