The 12 card propaganda bonus: counts the same as starting vault? So cannot take 12 Fireflies and then take 12 more with propaganda bonus, for a total of 24, correct?
Correct. Propaganda bonus only means you have a bigger starting Vault. It doesn't bypass the Vault card limit.
Note: this rule differs from what we had during last War when propaganda bonus was given
after round one, and the starting Vault limit no longer applied.