Each individual has their own way of studying and consolidating their knowledge. Some people may write notes to help cement their knowledge, whilst others may dive straight into past papers. It varies from person to person and essentially comes down to personal preference ie. Do what works well for you. There is no X method that equates to a Y ATAR.
If you find that notes are a waste of time and past papers/questions are much more effective for you, then by all means do past papers.
No they aren't essential. What is essential is the prep that is most useful for you personally, and it's not necessarily writing your own notes. Others prefer using other people's notes and doing past questions, working on essay scaffolds etc.
Here's a quote from another mod that pretty well sums it up, basically the methods for people to achieve conceptual understanding and that differ, but;