You need to spend some time perusing the UW website. There are so many different issues you need to learn about. College is about choosing one or two majors (UW has no minors, btw) to become proficient in. You do not attempt to master all possible fields that interest you. Check on the Honors programs for L&S (Letters and Sciences) and Engineering. Check the required courses for a degree in each of these, including various majors. UW admits students to the university as a whole, regardless of proposed major. This allows you flexibility in changing your major once you are there and have college experience. Remember the saying “jack of all trades and master of none”- in college you will need to choose one or two areas.
A check of the caliber of many UW majors will find the school is highly regarded in many fields. This may be a ranking of graduate programs but the undergrads benefit from them as well.
You need to research your terms- STEM and liberal arts in particular. You need to look at the requirements not only for a major but for graduating from UW. You will find that regardless of your school/college within the university you will need various courses to meet breadth requirements in science, social sciences and humanities. The number of college credits varies for a BS and BA as well. This means having some literature, foreign language and social studies courses along with your proposed science based major.
Check on the requirements for admission to UW and the courses most accepted applicants will have taken. Most HS students will complete four years of a foreign language before attending UW. Most will have taken many of the most rigorous courses their HS offers. Look at the gpa and test scores (ACT, SAT) for the middle half of accepted UW freshmen (that’s the 25-75th %ile). See where you fit.
It sounds like you are just beginning to think about college and will learn a lot about how it works in the next few months.