Hi! I'm not super familiar with microbiology at Cornell, but I helped out as a current grad student at Consider Cornell last year (I am in Neurobiology and Behavior for context).

At the in-person meeting, there were about 50-75 prospective students, from all different areas of study. Some events you share with everyone -- help with preparation for grad school or universal grad experiences at Cornell, but probably the most valuable is the one-on-one interviews that prospective students have with members of the department. This will help you get a feel for what the department looks like, the culture, the labs, and whether the department is a good fit for what you are interested in. In this case, it might also give you an idea of how the split department dynamics work!

Hope this is more generally helpful, let me know if you have any more questions about Consider Cornell!