What fields offer most data science job opporunities?
What difference does it make? Nothing stops you from applying to all of them. The real question is, can you and do you want to write software or do you just want to analyze data? Pay attention to the job descriptions in this regard. Data analysts are typically expected to be strong in classical statistics, while machine engineers are expected to know ... machine learning. Then every field has certain problems that you need to be familiar with before taking the technical interview, such as recommender systems for media companies, and time series forecasting for business/finance. You can find out what they are by reading around and actually applying to companies. Expect several rounds of interviews, including mathematical and programming challenges (real-time or off-line), and questions about your research.

Once again, every field needs data scientists, so this is not a criterion.