It is important to be familiar with the syllabus and the content that matches each syllabus dot point, given that all types of questions can assess your knowledge of virtually any concept from the four topics. The effectiveness of attempting open book exams would depend on the specific goals that you aim to achieve by doing this. If by this approach, you are attempting to maintain your understanding of the topics in the meantime until you can prepare more substantially, which would involve a thorough review of the content, then this does not seem like a bad approach. Looking at the reactions to your post, it appears that fellow students share the same opinion as you.
Regarding English Advanced, you should consider your ability to retain and modify multiple pieces to suit the Module C question(s) that will be part of your exam. In any case, you should probably aim to prepare at least one piece of each type. I think it would also be important to note that you should prioritise the imaginative/discursive/persuasive pieces since you will definitely be required to write one in response to the particular question, whereas a question requiring a reflective response is not guaranteed to appear. Of course, this does not suggest that you should not emphasise reflections as part of your preparations, just that priority should be given to the more essential element. There was also a relevant discussion within an
earlier thread in which you might be interested.
I hope this helps!
