You should write the Task 2 essay first because it is longer and it is worth 60% of your writing grade.
You should write a minimum of 250 words, but you can write more words as long as they add and expand your ideas. Do not write repetitive ideas or irrelevant ideas.
You should spend about 40 - 45 minutes on this task.
Discussion essays provide 2-views on a topic; you must understand both views and how they are different.
The question usually states: "Discuss both views and which side do you favour?"
It is more academic and a better strategy to provide reasons for both views.