01 - Cook elbow macaroni according to package directions until al dente. Drain thoroughly and rinse under cold running water to stop cooking. Transfer to a large bowl and set aside to cool completely.
02 - In a separate medium bowl, whisk together mayonnaise, sour cream or Greek yogurt, lemon juice, Dijon mustard, garlic powder, salt, and black pepper until completely smooth and well combined.
03 - Add cooled macaroni, cooked shrimp, diced celery, red bell pepper, red onion, and chopped fresh herbs to the bowl with the prepared dressing.
04 - Using a large spoon or spatula, gently fold all ingredients together until pasta and shrimp are evenly coated with the dressing. Avoid overmixing to prevent breaking up the shrimp.
05 - Cover the bowl tightly with plastic wrap or lid. Refrigerate for at least 1 hour, or up to overnight, to allow flavors to meld and develop fully.
06 - Remove from refrigerator and give the salad a thorough stir. Taste and adjust seasoning with additional salt and pepper if desired. Serve chilled on a bed of fresh lettuce leaves.