NSHSS

Answered

Seems like you've gotten the info already, but just to be sure, NSHSS is the biggest of those scammish honor societies that reach out to a bunch of high school students every year to try and snag dues from them. They're next to useless for anything real — like all the scholarships they advertise are pretty worthless either due to small size or massive levels of competition (or both), and they don't matter much, if at all, to colleges. The only legitimate high school honor societies are NHS and the related subject ones (NEHS, NAHS, NSHS) — and being a member of those is legitimately advantageous for college applications, kind of as a prerequisite that schools will expect to see on an accomplished student's resume. (In general, no legitimate honor society is going to ask you for huge dues — like NHS is $15, while NSHSS and others like it usually ask for 75-90 bucks.)

I think this strongly depends on who you are and what the rest of your life/college application looks like. From what I gather from your EC schedule, you are already very involved. If you already have strong ECs and volunteering, NHS won't likely impact your application much because, as you mentioned, it's kind of a barometer of GPA and involvement with the community, which you've demonstrated in other ways.

I'm an NHS member through my school and in a similar situation as you are when it comes to EC involvement--in fact, NHS isn't going on my MIT application (max 5 ECs) or any of my Coalition schools (max 8 ECs) because I have other activities I value more and that say more about me than my NHS membership. The only school that will see NHS on my app is my state flagship (not a reach school) because they only take CommonApp and I had space. I personally know people who are barely hanging on to their NHS membership (and even one girl who paid her way in, oop), and honestly I don't feel as though colleges think everyone in NHS is top of their class.

Ultimately, it's a judgement call. NHS does have pretty steep time requirements (at least at my school), and you absolutely need to budget your time junior year between ECs, competitions, classes, and standardized tests. As a rising senior, I wish I had dropped NHS and one of my other ECs to spend more time on projects that I was more interested in, and that are actually making an appearance on my applications. If you don't have ANY volunteering otherwise and don't know where to find any, maybe join NHS. If you're worried about showing academic excellence through GPA and standardized tests, maybe join NHS. Heck, if you think you'd enjoy it, maybe join NHS. But if none of those things are true, it's probably a waste of time. Admissions criteria vary from school to school (re: paying your way in like the girl from my school), so NHS is more of a benchmark than an actual display of your abilities unless you do something unique with your membership by way of leadership or outstanding community service.

Most of my answer is absolutely anecdotal (good luck with your mom!) and it's hard to find a source that says NOT to join NHS, since there's really no way to be rejected based on it, but here are some links that basically reiterate what I said about it not being very impressive unless you're a standout member and that, ultimately, it's your call.

https://www.huffpost.com/entry/is-national-honor-society_n_3267251

https://talk.collegeconfidential.com/college-admissions/808736-does-national-honor-society-really-matter.html

Hope that helps!