Intel has an excellent illustrated guide to optimizing the depth tuning on the 400 Series cameras.
As for the default config ... I believe that on the default configuration, no filters are set. You can add your own configuration instructions to set up filters if you wish.
I could not locate any further documentation for the config instructions. I found a good method though for researching each instruction in a web search.
1. Start the search term with cfg. (cfg with a full-stop after it)
2. Immediately after that, put the name of one of the config instructions on the documentation link I provided earlier.
For example, to search for examples of usage of enable_record_to_file, search for:
Another way to set up a specialized configuration for the camera is to use a Visual Preset. You can either select these easily from the 'Presets' drop-down menu near the top of the options side-panel in the RealSense Viewer or call a specific Visual Preset configuration from scripting.
Going even deeper, you can use the camera's Advanced Mode to define a custom 'JSON' file of configuration settings to load.