Whisk mayonnaise, red wine vinegar, pepperoncini brine, olive oil, Parmesan, Dijon, Italian seasoning, garlic powder, red pepper flakes, salt, and pepper until smooth.
Add shredded romaine to a large mixing bowl.
Fold in salami, ham, pepperoni, and provolone until just combined.
Add tomatoes, red onion, pepperoncini, and olives.
Drizzle over about two-thirds of the dressing and toss to coat evenly.
Taste and add more dressing, salt, or pepper as needed.
Serve right away, or chill 10 minutes to let the flavors mingle.