Honestly, I never thought about the "rules" of how these words were used... that's just how we talk in much of Texas (and probably other places). I can guess that "out" meaning west is because in early American times, going west was dangerous. You were going "out" of safety and into the wild. Going "over" just meant going horizontally on the map but within an established (safe) area. Up and down are kind of obvious,…
I use y'all in slack/email within the company I work at and correspondence with just about anyone (I live in the Northeast, but still use it), but I save "all y'all" for my closest friends, even though they might not have grown up hearing it.