epq is good practice particularly for essay writing and referencing skills. you won't need a whole lot of those studying maths or cs, but you could do an artifact epq and make it a coding project
coding projects aren't really a thing i'd consider a distraction from education. if you enjoy programming you'll find it easier to work on something and in turn uncover some of your interests in cs (hopefully). they'll be a good but minor addition to your personal statement though, and won't weigh heavily in the strength of your application
i'd suggest doing a coding project as an epq, and looking at some typical coding projects that people your age get started with (basic website development, discord bots, etc.) to do in your own time