Prepare the Dressing: In a small bowl, whisk together the sour cream (or Greek yogurt), lime juice, olive oil, cumin, chili powder, salt, and pepper until smooth.
Combine Salad Ingredients: In a large mixing bowl, add the chicken, black beans, corn, diced red bell pepper, red onion, cherry tomatoes, avocado, and cilantro.
Dress the Salad: Pour the prepared dressing over the ingredients and gently toss everything together until well coated.
Garnish and Serve: Sprinkle cheese on top and finish with crunchy tortilla strips or chips if using. Serve immediately or chill until ready to enjoy.