Even configuring PAM to get what I wanted to begin with was somewhat of an ordeal and took a few tries where I locked myself out of the system as I was building it before I eventually got it right.

Also my problem wasn't really pacman either. It was full disk encryption.

Understanding how PAM works is a source of confusion, and the documentation is almost non-existent and tribal. That part is very true.

But, after understanding it once, I found the process very intuitive and logical, to be honest.