Steam probably dominates the gaseous content forming characteristic bubbles that we see rising in 'boiling' water. 'Bubbling' will decrease the available surface area of liquid water lining the bottom of the container vessel, until the rate of heat input absorbed through the water volume bound, as a mass of matter, in liquid state (a molar mass amount), versus the water which changes state into translucent 'steam', reaches an equilibrium with the rate of heat input over the heat exchange surface area. But I don't think 'steam' is an insulator... too many people have been badly disfigured by super-heated translucent steam scalds.
The clouds of white stuff is water vapor, just like weather 'clouds' can produce rain when they are forced to rise on prevailing air currents across hills, and mountain ranges. The vapor mass loses energy through its expansion at higher altitudes (with lower atmospheric pressure) and condenses/contracts as this energy drop precipitates a phase change back to clearly bounded lquid water. I think this is fluid dynamics.