Details of styling and options can be found on the Superfish plugin page, but an example of how you might change the menu behaviour might be
<ddr:MENU MenuStyle="Superfish" runat="server">
<ClientOptions>
<ddr:ClientString Name="speed" Value="slow" />
<ddr:ClientOption Name="animation" Value="{width:'show'}" />
</ClientOptions>
</ddr:MENU>
which looks like this: