Choosing from NYU BU UCSD or Emory Oxford after being admitted

Just got admitted by NYU BU UCSD and waitlisted by Emory University Oxford college. I am an international student from China and want to major in BME to go into medical school. My family members are all in China so the location won’t be a huge factor. Since I got accepted by Mathematics/applied science major in UCSD instead of Bioengineering so I wonder how does transferring into bioengineering work and are there any downturns of transferring major. I went to visit NYU and BU and really like the campus of BU. P.S. didn’t get any forms of financial aid from any of the schools.

No specific major is necessary for medical school in the US (but being an international student will make it more difficult).

UCSD bioengineering is an impacted major with capped enrollment, so it may be difficult to change into it after enrolling.