I deleted my previous answer as it was assuming undergraduate admission.
Assuming graduate admission, and assuming an MS in Engineering (and not say an MBa or Art History), then pretty much everything you mentioned would not count for much. Maybe a little bit, but they would not make you stand out. Graduate degrees are research degrees, so the only thing that will make you stand out is research experience, or deep technical knowledge that will give you a high potential of successful research.
The biggest thing that would stand out is published research. Peer-reviewed scientific articles in well known journals or conferences. Research experience in a lab that did not directly lead to a publication is also good, but not quite as much.
Co-op/internship at companies closely related to your desired research field (e.g. if you wanted to go into Aerospace Engineering, an internship at Boeing or Airbus would be good).
Extra-curricular activities that are closed related to your desired research field (e.g. if you wanted to go into Automotive field, membership on a team like World Solar Challenge could be good. If you wanted to go into Machine Learning, then participating in one of these challenges could be good: https://eval.ai/web/challenges/list).
The first one, publications, is worth way more than the other two, by maybe a factor of 10.
So what should you do now at 16? Well, it is unlikely that you will be able to get any publications in high school. It does happen, but its extremely rare. The other two may be approachable, if know you what you want to specialize in. But six years is a long time, you might change your focus between now and then.
So for now, I would say take things one step at a time. Focus on things that will get you into a very good undergraduate institution. In two or three years you can start thinking about graduate school.