Cook the macaroni: Bring a large pot of salted water to a boil. Cook the elbow macaroni according to the package directions until tender. Drain well and rinse under cold water to cool.
Make the creamy dressing: In a large bowl, whisk together the mayonnaise, Thousand Island dressing, sour cream, relish, mustard, apple cider vinegar, sugar, garlic powder, onion powder, salt, and black pepper until smooth.
Add the vegetables: Stir in the red onion, celery, and diced pickles.
Combine: Add the cooled macaroni and shredded cheddar cheese to the bowl. Gently toss until everything is evenly coated in the creamy dressing.
Chill: Cover and refrigerate for at least 1 hour before serving. This gives the flavors time to blend.
Serve: Give the macaroni a good stir before serving. If it seems a little dry after chilling, mix in 1–2 tablespoons of mayonnaise or Thousand Island dressing to loosen it up.