Preheat oven to 400 degrees.
Spread chips in a single layer on a large sheet pan.
Sprinkle with one package shredded cheese.
Add another layer of chips; top with shredded chicken and second package of cheese.
Bake until cheese is fully melted, about 7-8 minutes.
Remove from oven; top with bacon, lettuce, tomatoes, and green onions.
In a small bowl, combine sour cream, mayo, half & half, onion powder, and garlic salt.
Drizzle over nachos or use for dipping.