Moulton's article linked upthread looks like an explanation of his preference for certain seat tube and head tube angles, with a brief explanation of the reasons the bike industry produces the frame angles it produces, and how these differ from Moulton's own. It's readable, short and not too technical.
Like the OP, I've found the articles I have read get deeply technical, when all I wanted was concise definitions of the concepts with simple explanations of what happens when you 'push the envelope'.
I find most new road bikes uncomfortable and I have only recently got an understanding of why, in terms of their frame geometry; this has helped me find frames suited to loaded commuting and slow-paced day rides.
Unless this already exists on YACF, I'd contribute to a thread of simple definitions plus examples, if that would help. I'd probably learn something from it myself.