Preheat oven to 400°F (200°C). Line a rimmed sheet pan with foil or parchment.
Brown the meat, if using: In a skillet, cook ground beef until browned. Drain excess fat, stir in taco seasoning and a splash of water, and simmer for 2–3 minutes.
Assemble the nachos: Spread half the chips on the tray. Sprinkle with half the cheese, beans, meat, and jalapeños. Add another layer of chips, then repeat with remaining toppings (except avocado and fresh garnishes).
Bake for 10–15 minutes, until cheese is melted and bubbly.
Top and serve: Scatter with avocado, green onions, and tomatoes. Add dollops of sour cream or drizzle with crema. Sprinkle with cilantro and serve with lime wedges.