voreingestellt means default/predefined

Maybe it's better to say predefined, because most of the time it will not be the same path.

For example, during the setup process (i.e. probably the installation of a program), the setup wizerd will offer you a path like "C:/program files/this program" and this path always changes depending on the program you wish to install.

Vorschlag in your second sentence refers indeed to the Pfadangabe. It means that you can accept the specified/predefined path without changing it. (Vorschlag actually means proposal, i.e. you can accept the path that was suggested without changing it).
Mostly, when you install a software, the path they offer you is the one I mentioned above, so you don't have to change it, unless you have a different directory for saving program files.

I hope I managed to explain it clearly. It is very clear in my head, since I have also worked as a programmer and made a few installtions myself. I hope I could at least put you on the right track.