Make the Lime-Chili Sauce: In a small bowl, whisk together Greek yogurt (or sour cream), mayonnaise (if using), chili powder, lime zest, and lime juice. Stir until smooth and set aside.
Cook the Shrimp: Heat a skillet over medium-high heat. Season the shrimp with salt, pepper, and chili powder. Sear the shrimp for 2-3 minutes per side until pink and slightly golden. Remove from heat.
Assemble the Bowl: Divide the cooked rice or quinoa among serving bowls. Top with shrimp, diced mango, sliced avocado, and fresh cilantro.
Drizzle and Serve: Drizzle the lime-chili sauce over the bowl and serve with lime wedges for extra zest. Enjoy!