The physics should be set exactly as you want them before trying to edit the particles. Because the editing is set up to be a final thing. Any change you would want to make to the physics would cause you to loose all your hard work in editing them just to fix something.
I suggest making sure you have all of your physics exactly how you would like them, then spend good time editing the particles and adding a softbody to the particle system if you like. But I believe that a softbody is really only useful for animation, because in a still you can just edit the particles into the shape you want them.
Hope this helps!