How significant are non academic extracurriculars (like winning national awards in rubik's cubes)? Thx

Firstly, let me clarify the meaning of extracurricular activities. Extracurricular activities are non academic activities that a student is involved in outside of school. Academics oriented activities that a student involves in outside of school is called co-curricular activities.

Now, your question pertains to extracurricular activities. It does help boost your profile if you have been involved in competitive rubix championships for a long of period of time and have achieved major awards. Also, doing intriguing things like achieving Guinness World Records in cubing, or starting a local cubing club to help underprivileged children learn cubing would be helpful.

All the best!

EC’s are definitely an important part of your application. In most cases school grades and standardized testing are the most important components followed by EC’s, LOR’s and essays, however, if your achievements are at the global level then that could take centerstage. Often EC’s act as the differentiator between applicants because a lot of people have excellent academics but not all of them is a startup founder, or an international level sportsperson. So it actually depends on you whether you want EC’s to be a big consideration in your application.

ECs are a very important part of your application. They help you highlight your interests and the way you mobilize your efforts towards those interests. If you've had significant achievement across any of those activities, that's a bonus. Significant here would mean bagging awards at State, national or international levels. That puts you at an added advantage besides stellar academics and sets you apart from the rest of the applicants. While applying to the USA, HK or Europe, keep in mind that the universities are looking for a reason to select you and that would be decided by what sets you apart from the rest of the cohort (hence highlighting why diversity is an important factor in the admissions process).
You don't really need to do something out of the world; but achieving something distinctive even in something really simple can mean a lot to the admissions committee. Also, do not forget to include your explanation about how your extra curricular activities set you apart in your essays, provided you find the space to! (Don't just squeeze it in and make the essay go off topic).

P.S - maybe rubrik cubes can help the admission committee gauge your analytical and problem solving skills in a creative manner? You just need to show this in your essays if asked! or in some other blank space where you could put something extra in:)

Good luck with your applications!