Hi, Smart Approach just means it will always choose the "Move Towards Player" option in its move route. By default, the normal Approach option has a 4/6 chance of moving towards the player, a 1/6 chance to move randomly, and a 1/6 chance to move forward. It does not change how intelligent each move towards the player is.
This plugin does not do diagonal movements, but I would think if you already have a plugin that does diagonal movements it would also work for this one as it is calling the default movement options.