My kid achieved in music at the national and even international level, simultaneously, in two disciplines (jazz and classical). When we totaled it up, it was obvious that they’d spent at least 40 hrs/wk on music, throughout high school. They also had top 5th% GPA in a good suburban public high school, and a 36 ACT. That was what it took to be admitted (EA) to a tippy-top.
I agree with above posters - so many applicants will list over 20 hrs/wk of ECs, and still have excellent GPAs and test scores.
Your parts of the application should focus on you, your hopes and dreams, your academic aspirations, why the school is the right place for you to fulfill those aspirations, what you bring to the school. If there is something that needs to be explained, get your guidance counselor to do it in his/her cover letter. If the issue was untreated ADHD, it should read something like, “John has excelled academically at the highest level since he received a diagnosis and treatment for (insert what you’re willing to reveal), which has allowed him to function at his full capacity. His academic record from (9th grade or whenever you were untreated) reflects his untreated ADHD, and is not representative of his academic ability.”
It’s always better to let the guidance counselor explain any adversity. Work with them beforehand, to make sure that they fully understand the circumstances, and that they’ve gotten it across in their cover letter.