1. Keep your 2.4GHz signals on the outside layers as much as possible. Avoid vias in those traces as much as possible. Put your less critical signals on the opposite side from the components to which they connect, and the critical signals on the same side as the components to which they connect. Ensure that the 2.4GHz traces have an uninterrupted reference plane under them at all times - no splits.
2. Balanced stackup means that if you start in the center of the board, the layers are symmetric top and bottom. The four layer stackup you mentioned is a balanced stack up. The one recommended by 'rogerynt' is not. It also suffers from probably unnecessary splits in the planes.