Preheat the oven to 350 degrees F (175 degrees C).

Rub beef and chicken with 2 teaspoons garlic powder and fajita seasoning; cut into 1-inch strips. Set aside.

Warm refried beans in a saucepan over medium-low heat.

Stir remaining 1/2 teaspoon garlic powder, salt, and lemon pepper into mashed avocados; set aside.

Heat corn oil in a deep skillet over medium-high heat. Cut tortillas in half, then cut in half again to make 4 triangular pieces per tortilla. Fry tortilla triangles in the hot oil in batches without overlapping until crisp; transfer to paper towels to drain. Repeat with remaining tortilla triangles. Discard oil; wipe out skillet.

Return skillet to medium heat; stir in beef, chicken, onion, and bell pepper. Cook, stirring occasionally, about 7 minutes, then stir in cilantro.

Layer tortilla triangles into a large baking dish; spread refried beans evenly over top. Sprinkle with cheese; evenly spread meat mixture on top.

Bake in the preheated oven until cheese and beans are bubbly, about 20 minutes. Randomly dollop tablespoonfuls of sour cream and guacamole across top; sprinkle with tomatoes and jalapeños.