Questions about studying at SNU/KAIST full time? (I'm from the US)

The following, in quotes, is taken from my Reddit post (due to the fact that CC won’t let me post links to other sites):

“Brief Background:
I am a high school senior (will graduate in May 2021) in the US. I want to study and get my bachelor’s in physics or (maybe) computer science in Korea. There are many reasons including: interest in the language, the history of Korea, the cheaper tuitions, and the culture shock and taking of a huge step to change who I am fundamentally (by living in another country). I know that it would be better for job prospects to study in the US, even at my own local universities, but I truly want a non-traditional route after high school. Yes, I know I can study abroad for a semester to a year during my university years, but I feel that being a full-time student in Korea will be a totally different experience. Basically, I’m looking for adventure. I have no knowledge of Korean, but of course, by wanting to study in Korea, I am willing to put in the effort to learn it while I’m there.
Here are my questions:
I am considering SKY universities in addition to KAIST; which should I prioritize given my circumstances?
Should I reconsider this decision? Are there any downsides to “non-traditional” route in wanting to experience new things?
I’ve heard some issues with classes at these universities being labeled as “English” formally, but of some cases where the professor will use Korean instead to teach. Are there ways to avoid this to get the most out of my degree?
I think it would be beneficial to learn some basic Korean before I arrive in Korea for my program (if I end up going there); how do I go about doing this?
I plan on applying to some universities in my home state (Colorado) in addition to my application to the Korean universities as backups; is there anything else I should do to prepare that I maybe haven’t thought of?
Any advice for this high school student which answers questions I haven’t thought of? It can be about life in Korea, first time experiences/struggles (from international students who’ve studied full time in Korea), dorm life, the academic situation, the admissions and visa process, etc. A brief (or detailed) summary of your path that you took to get to Korea is also helpful!”

I’ve received many comments saying that I should know Korean on an academic level or I will struggle throughout my 4 years there. However, I’ve discovered (after hours of scouring the internet) quite a few people on YouTube and Quora who’ve studied full-time at either SNU or KAIST and are from countries where Korean isn’t the official language (well, basically outside of Korea). Obviously, they’d have completed their degrees with the English courses available. I’m wondering, why would it still be a bad idea? Also, considering the fact that I am inspired (by those on YouTube and Quora that I mentioned and the stuff in my Reddit post) and committed, how would I go about executing this plan?