I do Science Olympiad, Robotics, You be the chemist, I am studying for a Ham radio license, head to head, math counts, I am a chief science officer for my school too. (Which means I organize the STEM events). I also play the violin. You'll find that if you do a lot of clubs, it's not too much, since math counts end when science Olympiad heats up. ( unless you make the math counts them, then you can't go to the science Olympiad competition since they are on the same days.) also, robotics can help you learn about your build event, like maybe how to use a wrench if you are in the battery buggy event. I was not the one who did circuit lab at the competition, but I was an alternate, and I still went to the meetings out of interest, so it helped me with Ham Radio.
you may only get 7-8 hours of sleep each night, but sleep in on the weekends!
Right now it's summer, so I would say practice so you are not rushing to learn everything when school starts.