In a large mixing bowl, combine the cooked, shredded chicken, corn, red bell pepper, red onion, and cilantro.
In a separate small bowl, whisk together the mayonnaise, sour cream, lime juice, chili powder, garlic powder, salt, and pepper until smooth.
Pour the dressing over the chicken mixture and stir until everything is well coated.
If using, gently fold in the crumbled feta cheese.
Cover the salad and refrigerate for at least 30 minutes to allow the flavors to meld.
Serve chilled, either on its own or in tortillas, lettuce wraps, or over a bed of greens.