Applicants (and their parents) need to eliminate the words “impressive,” “like,” “best,” or similar words from their vocabulary until after decisions are made. It is the rare application/course schedule/EC that will “impress” admissions. Perhaps the AO that read Malala’s application was “impressed” by her ECs, but she set the bar high. Students should do things that are right for them.
For the specific example, art portfolios are generally of the quality that one would submit to an art school. It is unlikely that the student that started drawing a few months ago is at that level. They can certainly list as an EC. They can write an essay about it if it works into the prompt. But a portfolio? Probably not.
There is an adage - the thicker the file, the thicker the kid.