A strictly "horizontal" type of chart structure tends to emphasize levels in the org in clear rows; a drawback is that you might quickly run out of room, left to right.
If you'd like variety and need to optimize space, make some levels of the org stack vertically.
To do this, you click the position above the shapes you want to rebranch, then go to the Layout menu on the Org Chart toolbar. Choose an option there, such as Left Hanging or Right Hanging. The rebranching will affect just the selected group.
The default structure is Standard, which applies the horizontal structure.