To a medium bowl add first 7 ingredients (pineapple through cilantro). Drizzle with lime juice and gently toss to combine. Season to taste with kosher salt and freshly ground black pepper. Set aside or cover and refrigerate if making well in advance.
To Make the Sauce
In a small bowl, whisk together sour cream, lime juice and zest, chipotle hot sauce and kosher salt until smooth. Cover and refrigerate.
To Warm Tortillas
Place a large piece of aluminum foil near cooktop. Heat a dry, heavy skillet over medium high heat until hot. Add one corn tortilla; cook 30 seconds on each side until softened and lightly charred. Transfer to aluminum foil and fold around tortilla to keep warm. Repeat with remaining tortillas.
For the Mahi Mahi
Meanwhile, season fish filets on all sides with salt, pepper, cumin and chili powder.
Heat olive oil in a large nonstick skillet over medium-high heat until shimmering; swirl to coat the pan evenly. Place Mahi Mahi filets in skillet in a single layer and cook for 3 minutes. Carefully flip and cook 2 minutes more. Add butter; once melted and sizzling, tip pan to one side and spoon sizzling butter over filets, for about 1 minute more, or until fish is opaque and flakes easily. Remove from Heat.
To Assemble Tacos
Top one warm corn tortilla with 1/8 of the Mahi Mahi and spoon on desired amount of pineapple mango salsa. Drizzle with sauce as desired. Repeat with remaining tortillas, arranging on a serving platter as you go. Garnish with fresh cilantro and serve with lime wedges if desired.
Video
Notes
I recommend wearing gloves when cutting raw jalapeños as the juice can be very irritating to skin.
If you want lime wedges, you'll need an additional lime.