So, for those who are interested in the history, this is what my instructor told me. The style I practice (Fujian White Crane) originated from the Tiger Crane combination. This style was past down from Grandmaster Ang to Dennis Ngo, but then at some point Ngo split from the Nam Yang group and set up his own school and organisation. He wanted to come up with a new name and so traveled to China, to YongChun village. They already had a YongChun White Crane style however, so he settled with Fujian White Crane instead. In terms of the style, and the tiger elements, they are incorporated into the white crane forms that differentiate it from the shaolin white crane forms. We also do have a pure Tiger form called "Tiger leaves its den" but it is very advanced which is why I haven't come across it yet.
As for the Southern Mantis, that is just a little bit extra on the side, for variety and to show the similarities between it and the crane techniques. We only do the most basic Mantis form, and otherwise focus on the tiger crane combination.
So, to answer the question on where it all originated, apparently it came from Hung Ee Kan, one of the 5 Masters who escaped the burning of the Shaolin Temple in the 17th Century. While in exile he joined an Opera group and in doing so encountered the Tee family, who used the Crane style. Hung Ee Kan was enchanted with the style and fell in love with the daughter of the family, Tee Eng Choon. They married and together developed the Tiger Crane combination. Hung Ee Kan was apparently also responsible for the development of Hung Gar, so they are all connected.