i install shop lighting ...among other crap for a living.
i have found that standard T8 florescent 8 foot fixtures that use (4) 32 watt 5,000 K lamps work best. The newer electronic ballast work to -20F without much warmup needed.
in most 30x40 shops i install 2 rows of 3 each. sometimes i install a 3rd row for the guys that want LOTS of light.
these fixtures cost aprox $55.00 each plus the cost of lamps (about $2 each)
so far i have not seen any LED fixtures worth the $$$ to use. Ive actually stopped installing ANY led in commercial buildings due to their high driver fail rates ive been experiencing.
sure, the manufacturers give me a free driver to replace the defective one, but they dont pay for my labor. ive been eating too much $$$ lately. I regret ever installing them.
we have one local big time contractor that replaced all the towns street lights with LED a few years back. now all over town you look up at night and see major sections of these lights burnt out. 50,000 my aunts fanny.
the old style HID fixtures would last longer.
but enough of that ranting. as for the 3 separate switches..sure, good idea as long as your not like 80% of my clients and always flip on all 3 switches hehe .. all the time.
I have mine set as each row on its own switch, and i actually use it many times with only turning on 1 row of lights.
the T8 32 watt fixtures say they require 140 watts per fixture. One 15 amp circuit can easily handle 9 of these fixtures.