Heat a large skillet over medium-high. Add oil, then corn. Cook until lightly charred, 6–8 minutes. Let cool slightly.
Whisk mayonnaise, sour cream, lime juice, lime zest, chili powder, smoked paprika, cumin, salt, and pepper in a large bowl.
Stir in red onion, jalapeño, and garlic until evenly coated with the dressing.
Fold in the warm corn and most of the cilantro. Let sit 5 minutes to meld flavors.
Mix in cotija and green onion. Taste and adjust lime or salt as needed.
Serve warm or chilled, topped with extra cilantro and a pinch of chili powder if you like.