How does Versatile Performance work with bonuses to the social skills?
An Orating Bard with the Imperious Bloodline Student of Humanity (Eldritch Heritage) gains a Charisma bonus to Diplomacy.
When using their Perform: Oratory skill in place of Diplomacy, does that Charisma bonus get added to the Perform?
No.
When using Versatile Performance you use the bonuses to Perform rather than the bonuses to Diplomacy .
However it's really easy to get ludicrous bonuses to the Perform skill, generally much easier than getting bonuses with the other skills that Versatile performance lets you replace.