Most Magnolia varieties grow to a regular shape with an open centre. They rarely need to be pruned for shade purposes. If planted in the right place, then Magnolias rarely if ever need any pruning.
Understanding the growth habit of your proposed Magnolia, will ensure that you plant it in a sittuation where it does not need any pruning whatever, and will reward you with years of blooms almost regardless of the weather. Almost for Magnolias sometimes fall foul of late or hard frosts. Such damage can rob you of flowers for a whole year, and no pruning of any kind will help other than to remove unsightly the dead blooms!
Some Magnolias grow into a wide bowl or chalice shape Magnolia x soulangeana, others grow into a large conical shrubs Magnolia soulangeana Heaven Scent, whilst some form a mass of branches and twigs but remain reasonably small and slower growing Magnolia stellata. A few are evergreen requiring different treatments if they are to be grown as wall shrubs!