Bring a large pot of salted water to a boil. Cook macaroni until just tender, 7 to 8 minutes.
Drain and rinse with cold water until cool. Shake off excess water very well.
Whisk mayonnaise, sour cream, mustard, vinegar, sugar, salt, pepper, and relish in a large bowl.
Stir in celery, bell pepper, red onion, and pimentos until evenly coated.
Fold in the cooled macaroni until well dressed. Gently fold in the chopped eggs.
Cover and chill for at least 1 hour. Taste, adjust seasoning, and sprinkle with paprika to serve.