Columbia SIPA Standard Resume

I’m an applicant to Columbia SIPA’s MIA program and have a few questions I was hoping someone can answer re the standard (not quantitative) resume…

The standard resume has no page limit and is ostensibly ~3-4 pages long on average (bc they ask for normal margins and 12 pt font). That probably fosters a lot of applicant resumes that are unnecessarily lengthy with a lot of irrelevant content. So, I want to make sure my resume is efficient - showcases my hard work, but relevant work.

I have a mechanical engineering background (in international development)… so do I include my engineering internships, research, and activities/leadership from undergrad, even if only a few are specific to international development? If everything that is “irrelevant” is kept out from my resume, it might look like I slacked during undergrad or have odd gaps during some Summers. I am also ~3 years out of school, so I have since then worked on relevant projects, activities, etc. Do I just highlight my 3 years of post grad work then?