Cook the pasta: Boil the elbow macaroni in well-salted water until just al dente. Don’t overcook—soft pasta gets mushy once dressed.
Rinse and cool: Drain and rinse the pasta under cold water to stop cooking and remove excess starch.
Shake off water well.
Make the dressing: In a large bowl, whisk together mayonnaise, Greek yogurt, apple cider vinegar, Dijon, and sugar. Season with 1/2 teaspoon salt and 1/4 teaspoon pepper. Taste and adjust acidity or sweetness.
Add the mix-ins: Stir in celery, bell pepper, red onion, peas, and herbs.
If using, fold in chopped eggs and cheddar.
Combine: Add cooled macaroni to the bowl and toss gently until everything is evenly coated.
Chill: Cover and refrigerate for at least 1 hour, preferably 2–4 hours. This helps flavors meld and the dressing set.
Finish and serve: Before serving, taste again. Adjust with a splash of vinegar, pinch of salt, or spoon of mayo if it’s tightened up. Serve cold.