graduate admissions - PhD program application - CV (3+ pages) versus resume (1-2 pages) in the US

I am applying to neurobiology Ph.D. programs in the US that focus on disease research.

I am seeking opinions on my personal situation regarding the decision to include either a resume (1-2 sides) OR a CV (multiple pages) in my graduate school application for the schools that don't provide me much space to write about research. I also want to know about whether or not I can include research experience blurbs in the CV.

Originally, after being told by most schools that allow up to 5 recommendation letters to only submit 3 and after being told not to upload anything in the "optional and additional uploads," I felt a resume would be better for my application. Less writing and easier to read for the admissions faculty. However, I know many Ph.D.students that have submitted CVs, and almost every school I'm applying to states that I can submit a CV.

I don't have that much to discuss, aside from 3 significant 2+ year teaching experiences as an undergraduate student and 3 research experiences (2 summer internships + home university research since I was a freshman). Unfortunately, I won't have a paper out for at least another year due to an ongoing study. I am also active in several clubs/honors societies. Thus, my current "resume" is 3.5 pages long. I could probably get it to 2 pages, but this is where you come in.

Would you suggest to expand even more, possibly elaborating more on my research experiences so that my CV is around 4-6 pages, or would you recommend to keep it as a brief resume? For the CV, can I include 4-5 sentence research descriptions after I list the knitty-gritty stuff (e.g. program, what I did in that research program in regard to career building, etc.)?

The main reason I ask this is that I'm slowly starting to figure out some schools give me absolutely no room to discuss research experience. For instance, Johns Hopkins allows me to write a single page personal statement while answering quite a few other large points; thus, elaborating on research is hard. Also, I just contacted Duke who had a similar case in their application, and the Ph.D. admissions advisor for neuroscience told me to include details about my research experiences in the CV or the optional supplemental uploader. Harvard told me not to utilize the optional supplemental uploader to further discuss my research, although they allow CV uploads.

Regardless, for some of these schools, I will need to at least include a few extra sentences about my research whether that be through the optional file uploader or a CV. Has anyone had this internal debate or has a strong opinion on the better option? Thank you!