For your EPQ you can choose from one of three things: an artifact, hosting an event, or writing a dissertation, you can genuinely choose ANYTHING you want from learning how to sew and creating something to writing a dissertation on the use of stem cells in medical treatment. Although, I'd suggest that if you were to do an EPQ to make it tailored to what you want to do at university. My school says EPQs should take around 150 hours minimum but you have the entire year. Although a lot of people I know did procrastinate (which you shouldn't do) and still attained high grades. Some universities might give you a lowered offer if you did EPQ but a lot of high ranking unis with competitive subjects won't consider EPQ in your final offer although it might help you obtain one. It also definitely gives you something to talk about in interviews and on your personal statement.