Bring a large pot of salted water to a boil over high heat. Add pasta and cook according to package instructions until al dente, usually about 8–10 minutes. Drain and run cold water over it.

In a medium-sized mixing bowl, whisk together olive oil, lemon juice, Greek yogurt (if using), and Dijon mustard. Sprinkle in garlic powder, salt, and black pepper to taste. Mix until smooth.

In a large mixing bowl, add the cooled pasta, grilled chicken, chickpeas, edamame, cherry tomatoes, cucumber, and red onion. Mix in feta cheese and sunflower seeds if desired.

Pour the dressing over the pasta mixture and toss gently until everything is coated evenly.

Cover the bowl with plastic wrap or transfer to an airtight container. Refrigerate for at least 30 minutes.

Before serving, give the salad a final toss, adjust seasoning if necessary, and garnish with fresh herbs.