Jackson and Longstreet were an interesting yin and yang under Gen. Lee. Generally, Jackson was more aggressive and Longstreet was more cautious. The Army of Northern Virginia did best when these two voices were in balance. After Jackson's death, two of his division commanders (Ewell and A. P. Hill) proved to be weak corps commanders.
That's what I am finding out. What made Jackson so important was that he had a great understanding of the purpose of war.
I am finding that Longstreet was very cautious and would rather fight defensively than offensively.
Jeff Shaara said that there was only a Gettysburg because there was no Jackson. Jackson would have taken the high-ground at Cemetary Ridge and Little Round Top.
There would have been a battle when Lee invaded PA, but it wouldn't have been at Gettysburg.