Weighted doesn’t matter in the sense everyone weights differently.
Your undergrad and your rank matter.
You want to be top 10% to have the “best” chance - but you need to find the right schools, not the highest ranked.
Your SAT is fine - I wouldn’t bother.
You should be the best you that you can be.
Continue in current ECs - take on more responsibility with tenure.
Focus on school.
Be a kid - enjoy your high school years. Giving them up in hopes of chasing something that technically doesn’t exist (a top 20 school - it’s just a magazine’s dream) - well that’s just silly.
The other thing you can do - start visiting local campuses. Large, small, urban, rural, etc. Figure out - what is it that I want in a college - size, environment, weather, religion, sports, greek life, etc. Figuring these things out now (with visits, not just what you think because often visits change your perceptions) - but figuring this out today will help you build a list tomorrow.