if CC will allow me ill try to answer those couple of questions, though i am a SOGer not a ScrOGer
the thread
SOG Poll talks about the size of clones taken, though the thread is obviously aimed at SOG, apart from the veg time i think this applies 100% to ScrOG as well. in scrog i would expect the uniformity of the clones to be much less important, as you have the training stage at the canopy to even things up. if one plant is growing quicker than the others you can just keep training it around and fill more space with it, the only important thing being to fill the screen
as to the difference between SOG and ScrOG the difference is in the training, with scrog the screen marks the canopy height and the grower has to spend some time tucking and moving the growing tips to fill the available space.
with SOG theres simply no veg and no training, just freshly rooted clones put straight into flower. theres no canopy as the plants start off as very small clones, its your medium with colas growing out of it. instead of the scrog setup which is medium-stem-canopy-cola.
ive never tried ScrOG so please correct me if im wrong people, but i think ive read a fair bit about it on the board