What may look "not nervous" to you is probably the exact opposite of what the snake is feeling. If the BP is doing nothing but sitting in its hides, chances are it is as happy as can be. If it is cruising around its tank constantly, it is probably not happy.
Feed what is convenient and works for you. If you can feed live food and get it regularly, then that is fine. Most snakes have no problem switching to F/T though.