my advice for maths is to really understand where everything is coming from. it's one thing to learn a method, but there's a high chance you'll forget it if you don't understand it's roots or what it's actually doing. you need to be able to know how to tackle questions rather than learn methods and hope for the best because a lottt of questions are application. how to revise? there is only one way at this stage - past papers. every single one you can get your hands on - you'll start seeing patterns in questions and understanding what the exam boards really like to see. you need to work under exam conditions too, with real past papers to get a gist of the environment in the exam hall. youtube videos are really good too like you said, for consolidating knowledge!
especially for mechanics, understanding what is actually going on is so useful in a question, rather than memorising methods. this will take a lot of exam practice, but all i can urge you to do is exam practice! that's the best way to revise maths honestly.
well done on the As in physics and econ!! i feel like we're quite the opposite, i struggle more with physics 😭
good luck! i'm sure you'll get the A*!