Valiant abilities will resolve before the spell or ability that caused them to trigger.

If a spell or ability you control has one or more of its targets changed to a creature you control with a valiant ability, that ability will trigger if that creature hasn't yet been the target of a spell or ability you control this turn.

If you create a copy of a spell on the stack and target a creature you control with a valiant ability, that ability will trigger as long as the creature hasn't yet been the target of a spell or ability you control this turn.