Choose the branch you want to keep and remove the other one. If a young tree is properly trained, it will require little pruning when it is mature, except to remove damaged wood. Topping is never a good idea. It stimulates strong, short growth or water sprouts, which are susceptible to disease. Topping mutilates, weakens and kills trees.
Trees grow from the tips.
A branch that grows four feet up the trunk will always be at this height. It will not be higher as the tree grows. If you want to walk under your tree, do not let low branches develop. However, young trees do better if lower branches are left to help the tree become established. In two to three years, unwanted lower branches can be removed.