Preheat oven to 375°F.
Combine vinegar, water, salt, sugar and peppercorns in a small pot. Bring to boil and stir to dissolve the sugar and salt. Place celery, carrots and onions in a jar or small bowl and pour pickling liquid over to quick-pickle; cool.
Arrange bacon on a slotted pan or on wire rack-lined baking sheet and bake to very crisp. Cool and chop into 1-inch pieces.
Place eggs in a small pot, cover then with water and bring to boil. Turn off heat, cover pot with a lid and let stand 12 minutes. Crack eggs and let cool in cold water before quartering them lengthwise.
Heat a cast-iron griddle or large skillet over medium-high heat. Season the chicken with salt, pepper, garlic, onion, paprika and cayenne, and drizzle with oil. Grill chicken 6-8 minutes, turning occasionally, then remove to a cutting board and cool a few minutes. Thinly slice them across breast.
Whisk up salad dressing and transfer to a small pitcher or gravy boat.
Across a very large cutting board or serving platter, arrange lettuce. Line up remaining ingredients in rows across the greens: tomatoes, bacon, scallions, chicken down the center, pickled celery, blue cheese, drained pickled carrots and celery. Pour Buffalo Ranch dressing evenly across everything and serve.