Client-administered policy naming which side's collection funding configuration is authoritative after the Payer links. While unlinked, the Client-supplied configuration is authoritative. AlwaysPayeeAccountSupplied and AlwaysPayerAccountSupplied consult only the named side; PreferPayerAccountSupplied consults the Payer-supplied configuration first and falls back to the Client-supplied configuration when absent. The fallback unit is the indivisible funding-authorization pair, never a per-field merge, and revoked authorization is invalid under every value. This selector does not enable invoice auto-pay. While unlinked, collection uses Payer.isAutomaticInvoiceCollectionEnabled; linked-payer auto-pay uses Payee defaults or PayeeEngagement overrides. Changes apply to new collections only; in-flight reservations keep their snapshotted pair.