When he pass rushes as a LB, envision a 3-4 when 1 OLB rushes and one drops in coverage except the one dropping in coverage is really a 4-3 type off-ball LB.
Occasionally they would drop a DE into shallow zone coverage to just have 4 pass rushers. Often that was a DE lined up at DT in obvious passing situations.
Quinn does not stay the same every year. He is known to make scheme changes from year to year. Similar to Belichick in that regard.
Quinn went into last season hyper-focused on being a dynamic pass rushing defense. After giving up 240 and 207 rushing yards to the Bear & Packers, he made some scheme modifications. Much more read and react by the DL and much less stunting.
Also, he changed LVE from a stack and shed LB to run and hit LB. Similar to a DL 2-gapping vs 1-gapping. It's the reason fans/media believe that LVE in his 5th season and with no change in health/injury status magically went from "sucking" to playing really well.