I came 10th out of around 120 students in a top 20ish selective school this year for advanced.
I'm pretty sure I'll get a band 6. As for not reading texts, I read my AOS texts and Mod B texts a couple of times since they were both really short. I skimmed 1984 in about 2 hours twice, once before trials, once before HSC and read sparknotes + shmoop chapter summaries and a lot on context instead. For Mod C I rushed King Henry IV about a week before the HSC and wasn't bothered looking up summaries so I mostly worked off my teacher's explanations in class.
I definitely wasn't naturally good at English either, I consistently got around 10/20 in my junior english essays. Can't say anything about extensions but I'd guess the same applies.
But, I would advise that you read all your texts unless you're a massive procrastinator or have a few days left for an upcoming task. Since your HSC is ages away, I'd suggest you try read all your texts at least once as a bare minimum if you want to be sure of getting a band 6.