1) Its really up to you to decide how many plants you want to grow. Also depends on how big the rubbermaids are that you pick to use. Im Lst'ing six this time in mine.

2) For something you can stick in the corner of your closet and have it be unnoticable, any kind of yield is decent if you ask me.

3) Sog or lst is probably what you want to do because of the small space.