Well, about the types of journeys, usually the questions ask about how physical journeys could lead to inner journeys. In addition to that, they might ask you to discuss the types of journey presented in a text, in which I strongly suggest that you focused more on the inner journey.
As for the structure of an essay, frankly, I'm quite confuse as well. I've seen few samples (exemplar answers and band 5-6 samples). From my observation, I see that they answer the question first and then write down why it answer the question. They don't really summed up the plot of the story. They apply a particular event or chapter without discussing any form of plot. Probably better if you wrote down one or two sentences explaining how this is related to the question
Two techniques should be enough, I don't really recommedn three unless you can write quickly. I also have a question, would it be possible to say, use one technique and one direct quotation from the text? I've seen essays in 2002 HSC's note from the marking center that the students are permitted to do that.
Integration of essays should depend on the question, it should have links between one text to the other. You may link them with opening words such as similarly, as well as in... and so on.
For example:
Similarly, in the text (...), the journey leads to (...)
The texts should have links thematically. And as conclusion, you need to sum up the four text on how they answered the proposed question / thesis statement.
