I believe it would be a good idea to prioritise the preparation of draft discursive, creative and persuasive responses rather than preparing a draft reflection for Module C. This is primarily due to the fact that you may not necessarily be required to provide a reflection targeting your piece. This is the case of the 2021 and 2020 English Advanced HSC exams, where the former required a reflection in addition to a piece of imaginative, discursive or persuasive writing, whereas the latter only required a piece of imaginative writing that begins with the content of a specified extract.
Of course, the optimal approach would be to work on your writing skills in terms of your ability to develop good quality discursive, creative and persuasive responses (including drafts to those) concurrently with reflective responses that suit each type of writing. Given that trial exams can vary depending on the school/entity that writes them, they present a certain degree of unpredictability. Because of this, you may wish to consider following this approach with respect to your trial exam.