The only way that MixCast modifies your project settings is by adding project-wide script defines to enable further capabilities depending on your project's other enabled plugins (SteamVR, Oculus SDK, etc). This process is generally applied automatically on import, but for custom build pipelines, you may need to call ScriptDefineManager.EnforceAppropriateScriptDefines() if you've reset the active Script Defines in your build process.