I'm just pondering what size HPS would be needed for maybe 1-2 plants? I have a few small areas in a building maybe 2x4 or 4x4' area to grow in. Could you get away with a 250w in that area or would a 400w be better?
Your point of view is so wonderful, and I feel very interesting. I have a lot of immature idea where you get the answer, I will continue to focus on your posts, I hope you can continue to update, I will put my views and ideas to share with you.
For two plants, I am going to assume you are after a low-profile grow.
#1: grow a pure indica strain because it is going to flower a lot earlier and it won't get too monstrous.
I would use a 150W CMH (Philips Ceramic Metal Halide) lamp hung vertical, no reflector, between the plants. Prune judiciously to keep leaves a minimum distance from the lamp. Line the walls with Mylar film for maximum efficiency. The CMH runs a lot cooler than the HPS and radiates most of its light sideways. Far nicer in every respect. I'm using one in my GH to help control veg time, because it looks a **** of a lot more natural than a bright yellow HPS!