Great that you have direct admit to UT Austin, I generally lean to direct admit situations.
I expect the BME adjacent JHU majors have fine outcomes, but don’t know that for sure and JHU’s outcomes data don’t show a breakdown by major….so call the career and ask about outcomes for those specific majors. https://imagine.jhu.edu/first-destination-outcomes/
JHU isn’t going to necessarily equate to more opportunities or connections, there’s plenty of opportunity at both your choices (that you will have to work/put yourself out there to take advantage of and hustle to network), and you can major in what you want at UT Austin.