As far as science extra curricular....it is pretty easy to transfer scioly knowledge to other Olympiad’s and Science Bowl . Like you can use chem lab experience for Chem Olympiad, and BioOlympiad you can take from biology-themed events. I love the idea of Science Bowl - it’s legitimately a bunch of different scioly events mixed together. Also IESO, it’s pretty easy to get to the camp for USA(camp is harder if you don’t memorize rocks), I took the test solely from scioly knowledge and got in. As far as none Science extra curricular, literally just sign up for them and you’ll find the time, it just happens.
Don’t want to put the thread on too much of a tangent, but here it goes : How competitive is Science Bowl at Nats?