I often see university EAs aiming to do research projects to test their fit for specific cause areas. I don't think this is a good idea.
I think if you felt you were good or bad fit for a research project, either you were a good or bad fit for research generally or a specific style of research (qualitative, quantitative, philosophical, primary, secondary, wet-lab, programming, focus groups, interviews, questionnaires, clinical trials).
For example, it seems very unlikely to me that someone who disliked wet-lab research in biosecurity will enjoy wet-lab research in alternative proteins, but it seems less unlikely that someone who disliked wet-lab research in biosecurity will enjoy dry-lab research in biosecurity.
Similarly, if you enjoyed literature review based research in one cause areas, I think you are likely to enjoy the same type of research across a range of different cause areas (provided you consider the cause areas to be highly impactful).
I think decisions on cause areas should be made primarily on your views on what is most impactful (whilst avoiding single player thinking and considering any comparative advantages your background may give you), but decisions on roles / job types / work types should heavily consider what you have enjoyed and have done well.
I think rather than testing fit for particular cause areas, students should test fit for different roles / job types / work types, such as entrepreneurship / operations, policy / advocacy and a range of different types of research.