All the controls are functioning as promised. 
Auto mode adjusts the fan depending on air contaminants. A light display indicates level of pollutants. I did a quick test holding on open bottle of rubbing alcohol near the sensor. The unit promptly ran up to level three fan and red light. 
Night mode activates automatically when the room is dark. The unit is virtually silent. Only at the quietest time with very low ambient noise is the fan audible. Sometimes I override the fan speed one setting higher and even then the sound is a comfortable white noise.
Have to acknowledge Wayfair Canada Customer Service for outstanding assistance. Unfortunately two of the extra HEPA filter packages I ordered arrived damaged. Ashely and Suzanne seamlessly resolved the situation. Many thanks.