Umlaut, those specs are both for 4" panels, with one made from 703 and one made from 705.
6" panels will have better performance at lower frequencies, all else being equal. However, bass trapping is also about coverage area, so if you have a certain amount of material you're better off covering more corners with 4" panels. If you still have material left after all the corners are covered and you have your RFZ, then you can start making the bass traps thicker.
As far as spacing, a good rule of thumb is to have the space be the same as the panel thickness, ie, 4" panel 4" from wall, 6" panel 6" from wall.