I'm not sure where you are getting your information from but lemme give you my story. I applied for CS at Cambridge this year with 4 A*s in Maths, Further Maths, Chemistry and CS + A* in EPQ predicted. GCSEs were 8 9s and 2 8s with the 8s in two unrelated subjects. I got rejected from Cambridge despite all of this (granted I messed up my admissions test because of a stupid admin error that meant I only got half of my answers down on the answer sheet even though I had finished the entire paper in the question paper but I know so many more people who have done similar A levels to myself, done well enough in the admissions test to secure an interview but have still been rejected). So you deffo need strong A levels that link really well to CS to get in. The people I know that have offers all have either Physics or Chemistry - some do 3 A levels, some do 4 so you don't need to do 4 A levels but make sure it links to the course
@toomuchheaven . By all means, take French but if you are taking it, I would consider taking another A level with it because I don't think French will give you much credit.
So this is just Cambridge. I also got rejected from Durham because of "general competitiveness of the applicant pool". I'm not too sure what more I could have done other than achieving those two grade 9s I didn't get so it just goes to show how insanely competitive the CS courses are in this country.
I know someone who is doing Maths, Further Maths and Art in my year and they got rejected from Oxford, Imperial, Durham and have an offer from Sheffield (still waiting on UCL) so you do impact your chances if you do take an A level that doesn't really link well to your course.
Also, I know that you don't do CS A level and that it's not a req, but the fact that you don't do it and because you aren't doing an A level that links well with the course (French), it will severely impact your chances as you will be competing against other applicants who are doing 3 A levels and more that link well with the course.
As for doing an EPQ, that's going to add something but not much at the top unis to be completely honest. None of my offers have EPQ requirements attached to them and neither are there are grade reductions for it, should I get a certain grade in my EPQ. The only instance I'm aware of at a top uni that will reduce grade reqs is Bath (my friend has an offer that says that if they get an A in EPQ, they'll lower the grade reqs for their A levels by 1 grade). There may be many others that I'm not aware of but I'm sharing things from my own perspective so I can only tell you what I know.
Hope this was helpful.