01 - Prepare elbow macaroni according to package directions until al dente. Drain thoroughly and rinse under cold running water to stop cooking and cool pasta. Set aside.
02 - In a large mixing bowl, whisk together mayonnaise, sour cream or Greek yogurt, lemon juice, Dijon mustard, garlic powder, salt, and black pepper until smooth and well combined.
03 - Add cooled macaroni, cooked shrimp, diced celery, red bell pepper, red onion, and fresh dill or parsley to the bowl with the prepared dressing.
04 - Gently fold and toss all ingredients until evenly coated with the dressing, being careful not to break up the pasta or shrimp.
05 - Cover bowl with plastic wrap or lid and refrigerate for at least 1 hour to allow flavors to meld. Stir again before serving and adjust seasoning if necessary.