Let leaf temps and vpd tell you how high/low and how bright/dim the lights should be. As long as your grow area stays relatively warm (over 70f) the leaves should generally be cooler than the ambient temperature, if the leaf temps get higher then the lights are probably too low and or too bright. Do a little reading on vpd and you will learn how to collect some numbers that will tell you exactly the height and brightness that will be most beneficial for each plant at any given time.

Here is a good thread to get you started.