Yes, the files are unnecessary. I did this a couple of times already, removing those files except the compiled ones, the two mentioned above, before packing the mod for publishing.
You can unpack XC_Bags and take a look but you probably have Main.pak unpacked already, so look there. The Story directory of Main contains only the two mentioned files and several subdirectories. Don't change anything in the subdirectories, only delete the unnecessary files from the Story directory.
Removing the log file should most significantly reduce the mod's size, because the file is 40MB. The log file is for developers not players.
The log file is the reason why Baardvark's 6 man mod on Steam is almost as big as XC_Bags although it contains hardly anything more than the story code change, and some minor stat changes that are negligible in size.
All you need for mod editing are the definitions, which are in Story\RawFiles and the source code files which are in Story\RawFiles\Goals.
You don't even need the compiled code for editing, only for testing inside the editor. (And of course in the published mod, if you made changes ;-)
And more strictly speaking, you don't even need the definitions for editing, only for compiling ;-)
You can remove ALL files and definitions, leave the source files and still start the editor without problems. You'll have to create the definitions again though before you compile the code.
