Thje snake is usually packaged in a cardboard box labeled as LIVE REPTILE or something similar, with some form of insulation and ~2 heat packs inside, with the snake(s) inside a bag or container inside the box.

The safest way to ship (both for the snake and for legalities and insurance) is Delta Dash, which does require that you go to your nearest airport for pickup. Others do ship Airborne, FedEx, or UPS to your door, but they will not insure the animals, do not condone the shipping of reptiles, may open and refuse your package en-route, and no not guarantee delivery time or condition. That said, usually it's the packaging and not the service that determines the condition in which the snakes arrive and if you order from one of the big breeders like those you named above and are there to receive the shipment, everything should go just fine.