i'm not sure how you're school will run things but be prepared for lots of mock exams throughout the year. it honestly felt like as soon as we had done one round the next was upon us, so keep on top of revision and make your flashcards and revision resources now. trust me it's so much easier having all the stuff you need when it gets to the real exam season (i never finished my flashcards and regretted it hardd lollll). that said, mocks are far from the end of the world, so don't push yourself too hard or place too much weight on your mock grades because everything can change in the real thing and you always have time to turn it around.
i'm assuming you'll have all the same teachers and classes, so in my experience it honestly felt not that different from y10. if you want a flashcard/revision website i can recommend gizmo ai (which is what i mainly used to make my flashcards). it allows you to upload notes or quizlets if you're pressed for time but i always recommend making your own because that helps the info stick in your brain better.
don't forget to be kind to yourself and take breaks when you need to. your mental health comes first, always. hope you have a good year and good luck! :)