Here are some tools to convert the String files:
Check out this site. The Strings File Tool (.requires NET Framework 4) converts the text data files (STRINGS, DLSTRINGS, ILSTRINGS) to CSV format (UTF-8).
The XlsImport tool is for merging the data into a CSV/Excel file for better management. There's literally over tens thousand lines of text data, managing them within multiple sheets helps a bit.
There's some command line involved. Here is a brief explanation of how to use the packer and unpacker:
StringsUnpacker /DL [DLSTRINGS file to unpack] [Output filename and extension]
StringsUnpacker /IL [ILSTRINGS file to unpack] [Output filename and extension]
StringsUnpacker [STRINGS file to unpack] [Output filename and extension]
The packer works the same way.
E.g., StringsPacker [Filename and extension of data you want to pack] [STRINGS file to pack to]
There's a readme file in each of the two zip files that go into more details (in Japanese, sorry) on the commands and format.
If that's not your thing, try this utility, requires MSVC (chances are you already have this installed).
The best way to solve your problem is to unsubscribe from the Mods. In this way, Skyrim Launcher will no longer download them automatically.
To unsubscribe them, you needs to go to 'Data Files' on your launcher, then click on Skyrim Workshop and login to the Workshop.
From there, you should see your display pic at the right hand bar. Click on that, then click on Subscribed Items. You will see all the mods that your're subscribed to. Unsubscribe from those that you don't want any more.
You were unable to get rid of them previously from the 'Data Files' tab because all the mods are linked to your account. You have to manually remove them from the Skyrim Workshop.
I hope this helps! :)
Best Answer
Like Fambida wrote in the comments, "data files that aren't contained in an esp or esm file." - an example would be some added/changed textures like this mod: http://www.skyrimnexus.com/downloads/file.php?id=193 -- basically a couple of .dds files