I never used netcfg (I assume you mean the utility found in http://netcfg.sourceforge.net/
) but in any ways there is no connection between KDE and the operating system's network configuration.
What you should be concerned is only that netcfg will be compatible with your distribution's configuration tools. If it successfully configures the network for you, and it doesn't collide with some other scripts installed by your distro - then you can use it. KDE and GNOME have their own tools also but those tools usually don't run on startup so they won't change any configuration you do manually or with netcfg.
Just try to see if it works.