The competition is basically a huge science fair, and there are no direct constrains on the projects you can submit, but there are several things to take into account. First of all, research has to be conducted entirely in a twelve month period, so already even the best participants can't do work equivalent to a masters degree. During the judging process, the real world impact is given much importance. This contrasts with an emphasis on basic science and theoretocal research - both approaches are fine, but this is a conscious choice. Finally, the judges generally don't actually read a long manuscript but rather rely on a poster and a quick 15 minute interview/pitch where you broadly overview your project - meaning that the competition wants to emphasize scientific speaking (this also is a boon to international participants who wrote their work in another language).

Because the scope of research one can complete in a year is so limited (and has to be balanced with school), and the amount of experience everyone has is small, the scope of the work can't really compete with academia.

Source: participated

I wonder: how much of the work done by those who reached the national level, will be used in some way in real products ?

How does this compare to real scientists/engineers success rate ?

Just out of curiosity - and of course i know it's not the goal here - but education/inspiration is .

You are correct. I do not know the complexity or the merit of the other competitors, and I might have made my comment based on my current knowledge of the technology involved (knowing that it is not very complex).