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2 x 300W will be fine and probably give better coverage.

480w/16ft^2 = 30w/sq ft.. only the most efficient lights on market will be up near high end of DLI. important note. You might need 23-25w/sq ft for autoflowers on an 18/6 cycle and probably closer to 34-35DLI over 12 hours and full power. Cheaper lights will be lower DLI due to more watts needed per umol/s of par produced (efficacy)

480w LED can do photoperiods in ambient co2. need a bit bigger if you want to supplementmore co2 with a tightly controlled environment. 480w over 18h is probably enough for autoflowers and boosted co2, though. reference a daily light integral table. using umol/s, your area in m^2 and hours of operation you can get a rough estimate of your DLI. 35-40 dli for ambient co2 and maybe 50-60 for boosted.. depends a lot on the other factors to maximize the co2. These are good starting points that may need anothet 5-10% adjustment based on observing how the plant grows.

Sure. But you probably don't need that much. I use 320 watt light in a 3x5x5.5 tall. It works perfectly. When I use a 480 it is just too much at full blast

Yes, in fact some people like myself prefer to do this. You are able to adjust the lights better to suit your entire grow. Sometimes I will flower different strains at the same time and inevitably one will be shorter than the other so I will raise and lower one light to suit the plants. I suggest getting a light that has a ballast that can be hung outside of the tent. So much heat comes from a ballast and if you can remove that from inside the tent the better off you will be. I hope this helps.