I don't do flowering rooms. My setup is so cheap and easy you'd probably puke.
Regarding light, you didn't mention the hood, probably the most important consideration other than the wattage. I'm partial to 600W, started the trend 14 years ago when no one had heard of them. That said, you should start small, get a feel for it, understand your program and then go from there. It's all in the balance, not any one factor, that's what I mean by "program". You must balance your light with your availability of salts and water. Penetration is over played here, as is stuff like pH. In fact, my ladies never complain about my penetration, and trust me, it's not very deep.
The lowest leaves stay on until harvest, and the lights are a good 5' or 6' above the lowest branches.
What's really happening is folks are giving their plants high priced crap which induces premature leaf drop. If you understand plant nutrition, then you will have noticed that most cannabis specific foods aren't using correct formulations regarding the NPK values only using gimmictry such as amino acids, enzymes, vitamins and such to hawk their products. Why they sell this shit to their customers is shameless, but like they say, "a sucker is born every minute." The foods are too high in K and too low in N, especially what they try to pass off as a "grow" food for vegetation.
Good luck,
UB