Cook elbow macaroni according to package directions in a large pot of generously salted boiling water until al dente. This usually takes about 7-10 minutes. Avoid overcooking.

Drain the cooked macaroni thoroughly in a colander. Rinse immediately with cold water for 1-2 minutes to stop the cooking process and cool the pasta completely. This also prevents the pasta from sticking together. Let it drain very well, shaking the colander occasionally, to remove excess water.

While the macaroni cooks and cools, finely chop the celery, red onion, and red bell pepper. If using, chop the hard-boiled eggs.

In a large mixing bowl, whisk together the mayonnaise, Dijon mustard, apple cider vinegar, granulated sugar, salt, and black pepper until the dressing is smooth and well combined. Taste and adjust seasonings as needed for your preference.

Add the cooled, drained macaroni to the large mixing bowl with the dressing. Add the chopped celery, red onion, red bell pepper, chopped eggs (if using), and well-drained sweet or dill pickle relish.

Gently fold all the ingredients together with a rubber spatula until the macaroni and vegetables are evenly coated with the creamy dressing. Ensure everything is thoroughly mixed.

Cover the bowl tightly with plastic wrap and refrigerate for at least 2 hours, or preferably overnight, to allow the flavors to fully meld and the salad to chill completely. This is crucial for the best taste.

Before serving, give the macaroni salad a good stir. If it seems too thick, you can stir in a tablespoon or two of milk or extra mayonnaise until it reaches your desired consistency. Garnish with a sprinkle of paprika, if desired, and serve chilled.