Normally, most colleges require scores from one test: either the ACT or the SAT. However, for 2020 most colleges are test optional. If you have good scores then submitting them can help your application, but not submitting scores for any reason won't hurt you.

Most students do better on one test over the other, but it depends on personal preference. If you can, try both (before your senior year) and then focus on the one you're best at! Most colleges "superscore" tests, meaning that they look at your highest score in subsections across all the tests you took. That means it's best to take the tests multiple times!