There are some mods to make gameplay more enjoyable. You can find them in the guides section. It's mostly just stuff related to worker and equipment radius but it makes gameplay much more enjoyable and less frustrating. Also, the audio files are mostly OGG so you can replace them with other OGG files theoretically. I haven't tried myself so I don't know if they're that weird OGG format that's encrypted or not. Each add-on has it's own folder, though it shares files from the other folders of add-ons and the main game so changes you make will affect the other games/expansions too.