Bring a large pot of salted water to a boil. Add cubed potatoes and cook for 8–10 minutes until fork-tender but not mushy. Drain and allow to cool completely. In a separate pot, cook pasta until al dente. Drain and rinse under cold water to cool. In a small bowl, whisk together mayonnaise, Greek yogurt, Dijon mustard, apple cider vinegar, olive oil, and garlic powder until smooth. In a large mixing bowl, combine cooled pasta, potatoes, bell pepper, celery, red onion, cherry tomatoes, and parsley. Pour dressing over mixture and toss gently until evenly coated. Season with salt and black pepper. Refrigerate for at least 1 hour before serving. Stir before serving and adjust seasoning if needed.