It should be a straight 20' run from the panel to the wall, and then up 90º for a 3' run to the subpanel. So I'll have two 90º turns, one from the main panel to the main run, and one from main run to the subpanel. I was going to use an elbow like this below the subpanel to make the run easier to manage:
Does anyone know how high off the garage floor is code for a subpanel?