Preheat a grill or grill pan over medium-high heat.
In a small bowl, combine olive oil, chili powder, ground cumin, smoked paprika, salt, and black pepper.
Brush the chicken breasts with half of the spice mixture.
Grill the chicken breasts for 6-7 minutes per side or until cooked through and internal temperature reaches 165°F (74°C). Remove from grill and let rest for 5 minutes, then slice into strips.
Brush the corn with the remaining spice mixture and grill for 10-12 minutes, turning occasionally until charred and tender. Remove from grill and let cool slightly.
Cut the corn kernels off the cobs using a sharp knife and place them in a large mixing bowl.
In a separate small bowl, whisk together mayonnaise, sour cream, lime juice, minced garlic, cayenne pepper, and half of the chopped cilantro.
Add the dressing to the corn kernels and mix until well coated.
In a large salad bowl, combine chopped romaine lettuce, diced red bell pepper, sliced red onion, and the dressed corn mixture.
Top the salad with grilled chicken strips and sprinkle with crumbled cotija cheese and the remaining cilantro.
Serve immediately and enjoy your Street Corn Chicken Salad.