I found this article to be very interesting. It is very long. But I suggest scrolling down the page to see the various topics it covers. It may help you to address some of your questions: http://www.americanaquariumproducts.com/Aquarium_Lighting.html
I use a combo of T5s and blue LEDs. The blue actinic lights (and blue LEDs) will be able to penetrate to deeper areas of the tank than other spectrum's (same concept that happens in the ocean). My tank is a little over 26 inches deep, I use 6 T5s, and I grow these corals at the bottom of my tank around the sand bed: palawensis, seritopora, monti caps along with the usual lower light loving corals like chalices, favites, favias, duncans and acans. My next attempt is seeing how well deepwater acros do lower in the tank (1 out of 2 from MACNA is still going strong).
I tried out ATIs based on the videos below and I do love them.
https://www.youtube.com/watch?v=Y-TbkPJhHkY
https://www.youtube.com/watch?v=6OSS_PoUX6o
Currently running from front to back of tank:
ATI Coral Plus
RedSea Actinic (peaks between 440-460nm)
RedSea10,000K
ATI RB Special
ATI Coral Plus
ATI Actinic (peak at 425nm and again at 450nm)
Blue LEDs: one strip along front and along the back of the lights above (on 24 hrs/day)
I have a 10K bulb in the mix for faster growth of corals (http://www.advancedaquarist.com/2008/3/aafeature1).
Two different actinics to hit two different peaks in the 400-500nm range for better fluorescence.