Do I have a good chance of getting into my top university if I decide to opt out of the SAT or Act?

There is a big difference between test-optional and test-blind. When they say test-optional, that means that you are not required to submit it but colleges will look favorably on those who do submit it. If they say test blind, that means that they won’t look at the ACT or SAT Scores. Since you will be competing against candidates who have submitted ACT and SAT scores, it is best that you do take the standardized tests and try your best to ace them. Colleges love to see students who go above and beyond the minimum requirements. That is the kind of people who will succeed on campus, so my advice is to take the ACT/SAT scores and get a high score. If you do choose to not submit a test score, keep in mind that there will be increased emphasis on your grades and extracurriculars. If you can really shine in those areas, you will be competitive.