So after reading all the comments here...
After having a conversation with an adcom through email, where they asked me to clarify details of my app and then immediately sent me an interview invite after doing so, I decided to reach out in that same email chain from that adcom after the interview took place. To thank them again, as I did in the initial email response, for reaching out to me for clarification as it allowed me to put my best foot forward, and ultimately led me to the pleasant interview experience I had with them weeks later. The adcom responded enthusiastically in return with smiley faces and joy, stating that they appreciated it, and then stated "if I would like" I could write a thank you letter to the rest of the admissions team, and they finished by saying: "I will happily forward it to them 🙂". We were not given ways to contact them during the interview.
So, it appears I've learned a lesson here.. as I was previously quite tentative to send an email thank you, and in doing so now am in a position to ultimately write two. And for at least one member of the admissions team for that school, they appeared to approve strongly. What effect it will have on my admission at this point almost seems irrelevant, as customs and courtesies take precedence over any feelings I might have against brown-nosing.
As a side note, it really has been great to build a rapport with a member of an admissions team over a few months, and whether or not I get in I will certainly remember how supportive and decent they have been, both in these emails and during the half-day virtual interview. I see horror stories on this forum and reddit, and so far my experience has been nothing but fun and positive. Perhaps I'll feel differently in 6 months if I have no A's, but I really shouldn't, as they're just doing their job, and well.