Place potatoes in a bowl; drizzle 1 tablespoon oil on top, add garlic powder, and mix to coat. Lay out potatoes on a baking sheet.
Bake in the preheated oven until tender, about 30 minutes.
Heat the remaining oil in a skillet over medium-low heat. Add red capsicum, onion, corn, jalapeno, salt, and black pepper; cook and stir until vegetables are slightly soft, about 10 minutes.
Heat a griddle over medium heat. Cook tortillas, flipping halfway, until evenly warmed, 2 to 3 minutes. Divide tortillas among serving plates; fill with the baked potatoes and sauteed corn mixture. Top tacos with green onions and cilantro. Serve with lime wedges.