https://en.m.wikipedia.org/wiki/Pirah%C3%A3_language
There are also a ton of videos and blog posts on the subject.
Not much. It's mostly inference rules, just like in English use of pronouns. I's just more pervasive, pertaining to verbs, adjectives, etc... If we're talking about gendered living organism, then it's just a marker for that binary classification. Anything else, it's just baggage attached to the word.