Well the softness of light depends on the apparent size of the light source. 12" is small in comparison to a lot of gear, but bring it in nice and close to the subject and you can do some wonders. Though if you bring it in close the light will appear to fall off as it moves across the subject which is yet another effect.
My advice setup your studio and leave it set up. Ever day move the lights around, play with them, do things to them and take pictures of yourself or any willing models. If you come and ask us for advice you will KNOW what we tell you, but if you figure these things out for yourself you will UNDERSTAND. That makes the difference between a photographer who sets up their lights textbook style and ends up with a collection of images that all look identical, and a photographer who masters light to make whatever effect he/she wants.