light hanging distance and power starts with a suggestion but no matter how good that suggestion is, you must adjust based on plant growth -- node spacing is your guide. If too tight, give less. If too stretchy, give more. Once you have the growth exactly how you want it, take note of power and distance and start there in the future.
How much light a plant can handle per day is variable... Temp, RH and co2 levels can vary by season, and you may need to use your light differently if these variables shift too much.
wattage is a poor way to talk about this stuff... it's fine when you are familiar with 1 specific piece of equipment. DLI (daily light integral) is what matters. A good start is ~40 DLI based on total umol/s PAR production of the light used (this takes into consideration hanging distance and light lost to radiance or absorption into walls), but you are probably beyond that 'first' step and can just use resulting node spacing as described above. Understanding the gist of DLI can help avoid 80% of trial and error to fine-tune the light, but never avoids it completely.