All Wizards you control get +2/+1 and have flying, not just those created by Docent of Perfection or Final Iteration.

When Docent of Perfection transforms into Final Iteration, the instant or sorcery spell that’s on the stack doesn’t cause Final Iteration’s triggered ability to trigger.

An ability that triggers when a player casts a spell resolves before the spell that caused it to trigger. It resolves even if that spell is countered or otherwise leaves the stack without resolving.

If you control three or more Wizards while you control Docent of Perfection, it won’t transform yet. It only transforms while its triggered ability is resolving after you cast an instant or sorcery spell.