Chester i'm afraid I cannot answer your question about lighting but I'm sure someone else will know and pop in with an answer. I bought the light setup I was told to buy and never looked back....or studied about it for that matter.

You've discovered the joy of this.....there are a million different approaches from all theyway around and some of them seem to actually contradict each other. What I ended up doing was attaching myself (almost literally) to someone experienced and doing things exactly the way they told me (i grow hydro) and voila....buds and things really did appear right and left (and they were good too).

I believe there are several reasons that make folks decide when to switch their plants over...I discovered as do we all that these suckers don't really take off until you are flowering....they can easily double or even triple in size during this period and go crazy; jamming up every inch of your space and lighting so turning them earlier keeps the size down. It does indeed affect the amount of your yield but not the potency....genetics does that part be it a little or a lot of yield. Also some people have continual systems where the timing of the process matters...

As far as when to turn I turn mine in hydro at six weeks...did not wait for preflowers although some do...on my first grow I waited 8 weeks for preflowers and they never really showed and i don't rely on the preflowers to sex the plants anyway. It is recommended by some to wait to avoid stress to the plant and possibly hermie....amongst other arguments....I found the waiting around to be a waste of time for me.

You really can turn your plants whenever you feel they are aready....have seen folks veg for only 2 weeks or so (after two week seedling stage) ...it's a personal preference. Once you have gotten through this grow and seen how much more these things will shoot up in flower (I couldn't believe it the first time) it will help you decide in future grows how long to wait. Space restrictions have a lot to do with it. Good luck and keep us updated!!