I'm thinking of switching from the steam version to local copy so that I can keep playing if my internet goes down.
Aside from the main mod folder and [~/.config/unity3d/Ludeon Studios/RimWorld by Ludeon Studios/Saves/] is there any other place that hold files that I might need to keep playing the same save game.
You can play RimWorld even if your Internet goes down on Steam.
And if you are using mods, i recommend using Fluffy's Mod Manager (https://ludeon.com/forums/index.php?topic=16120.0) and creating local copies of the mods that you use...
So you can play them offline without any internet...