I am sure I want to send new information. The website says you can do so through the portal, but if I know who my regional representative is, would it be better or worse to email it to them? The portal upload thing just throws me off because update letters don’t really seem like “supplementary materials” in the normal sense. And, I feel like it’s more likely to be evaluated if it’s just emailed. However, an email could understandably annoy them.
@theorydebaeter - if the update is significant, I think uploading through portal would be the best, because they will attach to your application and will be available to whoever is reading your application. The regional reps are usually the first readers - who may have already completed reading your file. You want your update to be available to all, right?
Harvard tends to like applicants who follow instructions. 
See above.
See above.
They will read any update that comes through the portal. Don’t fear. However, as @MedSciBud says, the update should be meaningful. They really don’t need to be updated on a Perfect Attendance award, as an example.