What do the ECs of unhooked HYPSM admits look like on average? Yes, of course there are the ISEF finalists and music prodigies, but are they really representative of the average unhooked admit?
How many hours of ECs could one do per week before AOs get skeptical? For T10s, how many hours of ECs do applicants have per week on average (just based on your observations from your school)?
1 I doubt there is an "average". Someone could spend 20 hours a week on one sport, and someone else could spend 3-4 hours on each of three or four activities. Generally speaking, the impact you have counts more than what activities you do or the number of hours you do them.
2 My opinion... I read applications for a local scholarship. Kids overestimate hours all the time. I don't know if it is on purpose or if it is an oversight, but I will penalize those applicants either way. DD's high school sports teams practice for a maximum of 20 or 21 hours a week. I am skeptical of anyone who has more than a handful of hours above that in total, especially if they are taking AP/IB classes or a challenging course load. If you honestly do have an unusually high number of hours devoted to an EC (or two or three), it's safer to have a non-parent back you up on that claim.
3 Any activity that only meets for an hour or two a month (e.g. my daughter's two book clubs). These can be sources of great joy and therefore worthwhile to students who participate in them. However, they aren't likely to have a meaningful impact on the high school or on the community at large. They may or may not be listed on activities lists for colleges and scholarships, but when listed, they should be done so judiciously. If they are your ONLY activities, it will probably hurt your chances at highly selective colleges. Many high-performing students will have such activities, but will leave them off a college application, especially if it detracts from the picture they want to present to the college.