I speak 5 languages, with varying levels of fluency (English, about 50% fluent in Spanish and French, and about 30% fluent in German and Latin). Do I need to take standardized tests for these—like if I don’t, will it still be about as beneficial in admissions to elite schools?
Lots of applicants to elite colleges and universities are multilingual. Your level of fluency is not unique.
That said, it would definitely make sense to take SAT II tests or AP tests for at lease some of these languages because even if your scores don’t make a difference at admission time, they could well make a difference once you are enrolled. Depending on the college or university policy and on your specific score on an exam, you might have the foreign language graduation requirement waived and/or get advance placement into higher level classes and/or get course credit.