You use driver boards to control the current/light output level
The smart board that I am out of can set the LED to 5 different current levels with just a tap of the power switch.
The dumb boards I have can be set manually at a certain current level.
These high powered LED's do not run cool.
They are running huge amounts of current and require heat sinks inside the lights that transfer the heat to the outer skin of the light body.
The head heat from the light is not a problem, but you would not want to run the light on high unless you have air moving across the surface of the light to keep it cool
The head shot band around your head is hotter than the heat from the LED.
I like to wear the Headshots over the top of a ball cap or some other hat
I only switch mine to high when going downhill on the bike.
Most the time 25% power is more than enough for slo-mo activities
There are links next to all the parts on my catalog page that take you to the main info page for more detailed build info