its important that you have an area to keep a mother plant and to take and root clones and the same size area would probably be fine.
wouldnt worry about how many plants you use as a 150 only covers about 3 sq ft could possibly do 4 sq ft in a scrog okay, so its not going to require very many plants to begin with, it might be different if you was using a large light like a 1000 and covering 20 sq ft screen.
have seen many utilize lst and veg for a long time to get the plant ready to scrog wich does reduce there plant numbers but its not required if your willing to use more plants most all of your training is done in 12/12 if you run 1 clone per sq ft of screen you do not need to lst and can switch to 12/12 usually as soon as the plant reaches the screen.