Bring a large pot of heavily salted water to a boil. Cook the rotini until just al dente according to package directions.
Drain the pasta and rinse briefly under cool water until no longer steaming hot. Let the pasta drain for several minutes.
Pat the shrimp dry with paper towels. Toss with olive oil, Old Bay seasoning, and kosher salt.
Heat a large skillet over medium-high heat. Cook the shrimp for 60 to 90 seconds per side until opaque and gently curled. Transfer to a plate and cool completely.
In a medium bowl, whisk together the mayonnaise, sour cream, lemon juice, pickle brine, Dijon mustard, lemon zest, garlic, Old Bay seasoning, celery seed, kosher salt, black pepper, sugar, and cayenne pepper if using.
In a large mixing bowl, combine the pasta, shrimp, celery, cucumber, bell pepper, red onion, dill, chives, dill pickles, parsley, and celery leaves.
Pour the dressing over the salad and gently fold until evenly coated.
Cover and refrigerate for at least 2 hours, stirring once halfway through chilling.
Before serving, stir again and adjust seasoning if needed with extra lemon juice, salt, or a spoonful of mayonnaise.
Serve cold.