Sea of Green (SOG) is where you take a whole bunch of plants--sometimes as many as 4 per sq ft., don't veg them long, and flip them early. You end up with a bunch of single cola plants that will generally produce under an ounce. IMO, this is generally counter-productive. Plants will not flower until they are sexually mature, regardless of when you flip the lights. When you flip the lights early, you are simply depriving them of light.
Screen of Green (SCROG) is where you take fewer plants, you veg them for longer and train the plants to grow horizontally under the screen. This training should start while they are still young. There should be none to little foliage above the screen. Then when the plants start flowering, you let the buds grow up through the screen. Just putting a screen over your grow really doesn't make it a scrog.
I would suggest that you do some reading and studying so you understand more about the physiology of cannabis. Sexual maturity is generally denoted by alternating nodes and the appearance of pistils (or pollen sacs in the case of males). It generally takes 6 weeks when growing from seed. As you re running clones, they may have alternating nodes already--clones are the same biologic age as the plant it came from. This is the reason that you cannot clone autos. Even with clones though, I like to wait for the appearance of pistils before I flip.
Even if they are all supposed to be female, keep an eye out. You could get a hermy, especially if mom came from a bag seed.. I have also had a plant be 100% male that was supposed to be from a feminized seed. Never get complacent.
If you have an overcrowded tent/space, DO NOT top them. This just makes them shorter and bushier, a condition you do not want in an already overcrowded space.