So, for the data file you answered by yourself, it is usually read as json, xml,csv or text/dat file, and the data may be structured more than a config file.

However, on the other side the config file is the configuration file. It is like a text file but the pattern is in a particular format like key = "value"

Usually each key in entered in a new line, or if they are in the same line then they are separated by , (may be).

I think you need to process the contents of the files and then you can use above features. You can add your features as well.

Moreover, for the data, just browse your own computer for configuration files, i think its a good starting point,you can search for cnf,conf, cfg,.cf or ini files

1.There should be specifications for config files or you could restore it form config files. For example, json has {" and ":

2. Text mining could be useful if "a bag of words" available.

3. Structural information cold be used, for example, json could have standard indents.