Pep takes this easy! Different eras and Pep is waaaaaaayyyyyyyy advanced in the technique department.
I don't think that Young Griffo necisarily had good technique for his own era but he was still humiliating the best technicians of his era because he was so damn fast. Sort of like a miniture Roy Jones. This suggests to me that he would probably have done well in any era simply based on reflexes.
I don't think so. Griffo and Kid Lavigne were going to take part in the first filmed bout, but they refused when they saw the mini ring they'd have to fight in.
When Jim Jacobs hosted a film night in the early 60s in New York for invited guests, a clip of Griffo was shown - so we can't rule out the possibility, that it still exists somewhere.