The new version of the subcolumns extension is not made for updating existing projects.
With this version you are able to select from two buildin css frameworks, YAML 3 and YAML 4, but you are also able to add your own css definitions and use them with this extension.
You select the framework you want to use from the settings of contao. All the rest seems to be the same as in the first versions of contao.
For YAML3 and YAML 4 you can select in two versions each. The standalone is meant to be used with the Contao CSS-framework. You use the extended version, if you use the original YAML framework for oyur project.
In the next weeks I'll add more information, so you know how to add your own configuration.