Who tends to get better recommendation letters from school counselors? Does a small private schools gives better recommendation letters than a huge public suburban school? Does an active PTA mom’s kid better letter than an awkward immigrant mom’s kid? Does a popular athlete gets better letters than shy academic star? Does race plays a matter or school counselor’s personal bias plays a role?
Ok, you’re asking too many different questions to which I don’t have answers for. The general consensus is that letters should be from recommenders that know you well enough to support your application (not just repeating your resume or grades; but specific examples of your intellectual curiosity in class, interest in chosen field, involvement outside of school etc.) and should be from a variety of fields (1 Humanities/Social Science + 1 STEM seems to be commonly required/recommended, w/a supplemental, if allowed, from a job manager, music or art teacher etc. who knows you well.)
Above all, YOU get to choose who to ask for letters, so do a self-judgement of your performance in the class and your conversations with the teacher (if they’re overly busy/show a lack of interest or outright state they write form letters, you likely don’t want a letter from this teacher.) You only have ONE guidance counselor, on the other hand, so don’t annoy them!
Some teachers/counselors will ask you to provide them with short answers, specific examples from class etc. so take the time to be thoughtful and through when you’re providing these. You want to make it easy for your recommender to write their letter.
While a bad letter won’t make or break your application, especially to selective colleges, you don’t want to make it easier for them to not consider your application further.
Students at private schools likely have more detailed recommendations than those at LARGE public schools, but this is more a function of counselor case load than anything else.
IMO always waive your rights to view your letters under FERPA. It’s especially important at selective colleges where they value the knowledge that the letter writer is frank and open with their opinions of you. However, even if you waive your letter-viewing rights, there’s nothing stopping you from viewing it if your recommender offers the opportunity (as some teachers will do.)
Also, you did not need to include the phrase “awkward immigrant mom’s kid,” just shy vs. more social kid for letters would have worked. As the child of immigrants myself, please don’t stereotype. 
Hope that helps! Good luck with admissions!
How do you get to choose who fills out your school counselor recommendation? It comes from your school counselor.
OP - other than saying the better students/candidateS generally get better recommendations, there’s no way to give generic answers to any of your questions. Most of it comes down to the individual counselor and their experience/effort expended.
@RichInPitt That was for choosing teacher recommenders. I did clarify in my post that you only have one guidance counselor to write their counselor letter: “You only have ONE guidance counselor, on the other hand, so don’t annoy them!”
I would think schools with tighter GC connections are going to produce a higher quality LOR. My D’s private HS had the college GCs start working with their assigned students freshman year. The college counselors were also different than the team that did regularly counseling and course scheduling. By junior year, D knew her college counselor very well. They also had students fill out a 15 page “get to know me” type survey. We, the parents, had multiple meetings with the counselor including one on one visits during junior and senior year. There was a lot of actual guidance and review of the college list to be sure it was balanced. GCs also came to school events, sports, shows, and were very engaged in school life.
In contrast, our home public’s GC had over 100 students each and didn’t do any of the above. Students met with their counselor once in 4 years. I have to believe there would be a difference in quality and depth of the LOR.
I was asking about letters from counselors or principals, where you don’t have a choice. PTA and sports parents have great influence in local school here and they hang out with administration all the time so it raises questions among students about RL’s objectivity.
Same goes for private schools, with 4 counselors and 60 seniors, their letters would be more personal and detailed compared to public school with 4 counselors and 1000 seniors.
Very few colleges require a letter from the principal. A GC report is required. I suspect though that selective college AO’s know that there are vast differences in private school GC’s role and large public school GC roles. The letters that make more of a difference will be the ones from the teachers. That being said, students who are engaged with their teachers will likely receive stronger letters. Parents, might be a double edged sword.