How important was the existence of these war plans in bringing about the outbreak of war in july 1914?

A general European war would need a trigger, and this was provided by the murder of the heir to the Austro-Hungarian throne, Franz Ferdinand, Archduke of Austria-Este (1863-1914) and his wife Sophie, Archduchess of Austria (1868-1914) in the Bosnian capital Sarajevo on 28 June 1914.

None of the above, because the person who ruled TamilNadu at the time is Cheras