For the marinade: Whisk together lime juice, olive oil, cilantro, and chili powder. Pat Mahi filets dry and sprinkle with salt. Add fish filets to a bowl, cover with marinade, making sure the filets are coated. Marinade for 15-20 minutes.
In the meantime, create the Sriracha Slaw by whisking together Sriracha, mayonnaise, cilantro, and salt to taste. Add cabbage and mix to coat.
Heat large skillet over medium heat. Add 2 Tablespoons olive oil to pan. Remove fish from marinade and place skin side down in skillet. Cook for 6-8 minutes (you may need to cook longer, depending on thickness of filets); flip filets and cook for an additional 3-4 minutes. Be careful as some oil may splatter. Remove from pan and flake apart.
Layer Mahi Mahi and Sriracha Slaw on a warm tortilla and garnish as desired.