The 3-4 vs 4-3 debate is outdated as both assume 4 DBs, which that assumption is CLEARLY wrong in the current NFL as I'm pretty sure all 32 teams average using 5 DBs.
I just ran the numbers and the Packers average using
So the Packers used the 3 DL a maximum of 34% of the time... and some of that is false as at times a DL lined up a 4-2 DE... and Packers might at times used extra beef on goal line stands.
As for hard to find 3-4 OLB... it's said that Pettine likes those bigger 4-3 DE as OLB, because he likes versatility and those big guys can be asked to dive on the inside and becoming an extra DT on a given play (where there is then a free blitzer to the outside).
So Petite's scheme fits with those 4-3 DEs already
And Pettine's scheme isn't necessary press man... that's just what worked for the Jets CBs... he's cool with off man - man coverage if that works for a CB as well. As long as you cover the guy in one on one, he doesn't care what style you use.