Okay, this seems silly to make a post like this, but I wish I had found a page that told me this before wasting a few hours trying to figure it out!
For a while, I have been wanting my chatbox overlay in OBS to display newest messages at top and move down. Googling the issue only brought me newbie posts of "How to put your chat on your OBS!" and "One Billion and One overlay designs!"
Yeah, you can make your own custom chatbox by learning now to use the CSS and connections and what have you, but I like the layout and simplicity of StreamElements chat overlay feature (albeit, too simple somtimes). I have seen others with this type of layout, but its always been some other service, and I like to keep everything centralized to one service (that does emote walls, notifications,etc.), so it's always been a dead end.
So finally, I just sat down and dug into the CSS of the StreamElements chat preview and made some live edits to see what got me my results, and it boiled down to this: