Cook the Pasta: Bring a large pot of salted water to a boil and cook the pasta until it reaches al dente texture, following the package directions. Once done, drain the pasta and rinse it with cold water to halt the cooking. Set aside.

Prepare the Bacon and Chicken : Cook the bacon in a skillet over medium heat until crispy. If not already cooked, prepare the chicken by grilling, baking, or sautéing it until fully cooked. Chop into bite-sized pieces.

Make the Dressing : In a small bowl, whisk together the mayonnaise, sour cream (or Greek yogurt), and milk until smooth. Mix in the chives, dill, parsley, onion powder, garlic powder, salt, and pepper. If the mixture is too thick, thin it out by adding more milk to reach your desired consistency.

Assemble the Salad : In a large bowl, combine the cooked pasta, crumbled bacon, chopped chicken, half of the green onions, grape tomatoes, and diced cheddar cheese. Pour the dressing over the salad and toss gently to coat all the ingredients evenly.

Garnish and Serve : Top the salad with the remaining green onions and slices of avocado, if using. Serve immediately or refrigerate for at least 30 minutes to let the flavors meld.