Start at the bottom and work your way up. Give them time to acclimate to the lighting. I usually let them settle for a few days, 5 our 6, and depending if they are reaching for light or turning into hats, I'll move them as needed
Yes just look at stalk length to determine light requirements and if they have a clear appearance with short stalks they are too high up and bleaching.
I would leave mine in different flows once I found lighting and see which it responds better to. Take time in between moves to actually see a difference though. It usually takes me about a month before I find the perfect spot