@trjen21, It seems you have two separate but related questions: How to get into UCLA (and later its Architectural Studies major) and how to get into a good MArch program. I don’t know much about UC admissions, so I can’t comment on the best major to apply under.
On its website UCLA says this about their Architectural Studies program:
It goes on to say that admissions is “highly competitive” and that a portfolio is required. So whatever major you choose you need to make sure you can cover the pre-major courses and can build a strong portfolio.
It’s not entirely clear whether UCLA’S MARCH with BA in Architectural Studies, would be 2.0 or 3.0 years. Again, on their website they indicate that their BA Architectural Studies leads to “a preparation for accelerated graduate professional studies” which would indicate 2.0 years, but MArch programs can be quirky in their requirements.
My recommendation would be to reach out to the architecture program directly and ask them what “highly competitive” means in acceptance rate and how long it takes to get an MArch with their BA.
As a general statement you can get accepted into a top MArch program with a major in just about anything. A BA or BS in architecture or architectural studies is a common route, but your undergraduate major could also be studio art, art history, engineering or even something totally unrelated, like biology or history. MArch programs have different prerequisites; most require one or two courses in studio art, art history, physics and calculus. The portfolio is a big part of the admissions process.
Since you have another year to assemble your application list you have time to evaluate the different routes to an architecture degree, both the BA/BS+MArch and the BArch. It’s a complicated decision, not in the least because of the variable cost and time involved, so it’s good to start early on your research.