The elites want to see a certain number of APs, but after that number, they don't care. My D (now at UChicago) had 7 upon graduation, and my S will have 8. School systems that don't offer very many are not penalized as long as the student can show that they are ready for the rigor of college. The exception are places like Georgia Tech, which I consider elite for engineering, which care a lot more about the number of APs. But let's leave that aside for now.

I fully understand your concern re undergraduate credit vs learning opportunities. But IMO college admissions staff really don't know how to evaluate these learning opportunities, unless they are already well known, and therefore won't give it much "credit".

The way to get around that is to take these learning opportunities and then have your child put that learning to demonstrated use. For example, if it's a science course, follow that up with a research project in the same field.

It's been a number of years since I read Cal Newport's book, but one of the key points is that you want your child to build up a talent that is extraordinary for a high school student and that makes the admissions committee say "Wow!". This is why it's so important for the activity to be enjoyable.

I would also caution against applying for Tier 1 as an unhooked student unless you really know you are at the very top of your game. One of my son's friends this year is a 2xUSAMO qualifier and a Physics Olympaid Bronze medalist and attending one of nation's elite prep schools. He was deferred from MIT. It is brutally tough in Tier 1 in terms of pure merit.

That was the reason why we went with Tier 2 for my D. She had the grades and test scores, is a very talented artist and had multiple years of research as a lab assistant. But she never got a publishable result out of the research (in large part because it is a multi-year research project). Without that tangible thing that the admissions staff can point at, it was too big of a risk. Now, it turns out that she really did love UChicago, and by the time of her applications, it was her #1 choice so she went in for ED without hesitation.