Which is correct?
George starts to realize how many lives he has changed and impacted, and how they would be different if he was/were never there.
I think that here should use "if he had never been there"(past perfect) as this is the 3rd type of conditional sentence. Which means that it is an imaginary/improbable situation in the past.
in an other word, "If he was not existing in the past, the ones who were impacted would be different."