If you get all the details done, you can achieve for the most part, just growing tops.
How are less roots a plus? Growth below = growth above and vice versa.There is little foliage, and less roots. A good example of the opposite is growing aeroponics, you have all that root mass which is a waste.
I'm not sure I understand your reasoning with this...are you asking why one would use more/stronger light? More light is almost always a positive when talking about the plants production.Now if you run 600 watt bulbs then the canopy can be deeper, or should I say the buds longer in height before they hit the light but why do this?
I looked at growing as efficiency, and the equipment and genetics dictates everything else. The buds that fall too low under the light, or off to the side outside the perimeter are called nuggets, and sure they are not garbage. But I was trying to make a point here, you want to focus on the primary coala.
Just making a single cut to the main stem will result in two lesser mass colas, and the more you do this the less mass you get.
It is better to just get more plants, and add their mass up to get the amount you are going after.
To give you an idea, during the harvest of 38 plants only 18 inches tall yielded a little over 2.25 lbs. each and every time during the three years.