Like others said, good for you for starting and thinking about applications early! I’m pretty sure at least Andover releases some materials for essays in July, but I could be wrong. Definitely would not advise to take my route where I was still finding and researching schools in like October - November.
First, I don’t think you need to worry too much about sports, but I also may not be the most qualified to give advice as I definitely did not have the most outstanding results, but I did get into one of the schools on your list. I only put 2 sports on my application (if you’re counting dance as a sport bc ik its debated sometimes), volleyball and dance. Both of them were just on my school team. The main one I highlighted though was volleyball because I started in 6th grade and progressed a team each year and got an award at the end of my last season. Even if you didn’t earn a reward it’s okay, but highlighting any sort of progression can’t do harm! I did that through interviews mentioning my progression to higher teams and practicing a lot at home.
Another very important question that you will get asked in interviews is “Why boarding school”
I think for me I would not have been able to answer that question as well as I did without reflection, so I would say keep coming back to the question along the process after learning about the schools you’re going to. I also was somewhat forced to keep asking myself when adults would inevitably ask why I wanted to apply if I told them (usually happened when I asked for letter of recs which makes sense). If you need advice on how to answer it I can give you some, but you also said that did research and are comfortable with interview settings so if not fine by me!
You genuinely seem very qualified and I know how intimidating reading a bunch of threads on CC can feel as I was in your spot a year ago. You seem pretty well rounded which helps imo. Also remember that the AOs are looking to build a class (i’m sure you’ve heard this before), so part of admissions are also just luck. They may have a lot of applicants who do for example volleyball next year, or that may be exactly what they’re looking for if a bunch of their students who played volleyball graduated.
If you need more advice or have any questions just dm me, I’m happy to help!