The more vibrations, the more power.
The more differentiation in the mantras , less power unless if the runes mesh together well. Still no way to make up for the number of repetitions.
Incorrect way of vibration -a.k.a The rapper Syndrome - Spitting bars style vibration (without holding for some count and vibrating till your breath is out slowly and correctly FEELING the vibration with patience. ) - extremely diminished returns.
Lack of visualization and affirmation - diminished returns although will be made up by the number of vibrations and the correct form of vibrations.