That's a whole lot of question marks
I'll try to help a bit...
I, at first, thought, like you, that you should leave the plant alone and it'll grow best. But, with proper manicuring/trimming techniques, you can get better growth, and bigger buds.
The simplest explaination I can give is any growth that's unnecessary is a waste of the plants energy. For example, a large fan leaf on the inside of the plant isn't getting much light, and not really doing it's job, but it's still taking up water, that would otherwise promote growth toward the tops.
Smaller buds on the inside of the branches would otherwise increase production to the cola. I *think* if you trim a 1 gram bud off a lower branch before it forms, you'll gain a gram to the top. Might be debateable, but it's my opinion.
Your equipment is alright, a 1000W is as good as it gets for now, a bit more ventilation would be best.
I'd tie down the plants, and not trim anything off, that'll get light to the whole plant. The leaves and buds will grow towards the light, and you won't have any trouble with the fans blocking light.
How they're growing straight up, bend them over, they'll be fine, that's pretty much no stress.
As far as stressing a plant by trimming, it doesn't hurt it as much as it helps, I never notice a stunt in growth, moreover a burst of growth to where I want it.
Some of your plants seem to be overwatered, but I don't know really, that's why I asked how far away the light is, because they seem sorta small for their age. That would mean, possibly, overwatering, or light deficiency... Do you let the soil get pretty dry before watering? Not heavy to pick up at all?
Damn this is long
My bad.