A lot of the talk here about config files is regarding GPU crunching/tasks. You don't have any GPUs so that makes it easier. That would cover everything said about command lines and app_config files as well.

The cc_config controls BOINC and some things on communication with the servers as well. If you don't have issues, there is likely no need to look at it (or create one). But you can read the help files to see what options there are available.

IF your CPUs support AVX, you should use the Lunatics installer to install the AVX app. BOINC tells you the CPU features on startup, look for AVX in the list. I doubt your CPUs support it, but it is worth looking since AVX applications are faster.

That is the short version ...

The cc_config.xml and app_config.xml options are covered in the BOINC user manual, under Client configuration. That's your best reference source when you have questions like this.