This was a major release. With 1.0 and 1.1 live plugin was tested in different scenarios and combination of plugins and settings. There was good amount of information available for action.
Bug fixes were implemented in 1.1 so this release focused more on improving the plugin and loading it with new features.
The plugin sitemap creation time was reduced by optimizing query.So the query execution time is less.With less query execution time the plugin speed improved drastically.
Other major change was amount of memory consumed by plugin while creating sitemap.This issue was also addressed in this release. There is no instance of Memory problem reported after version 1.2 went live. The memory improvements performed in this release were the reason of it.
Though I still feel it can be made more memory efficient and execution time can be minimized.So minor changes are performed in each release.
Visual Composer plugin support was added in this release. Some users wanted the feature as they use Visual Composer plugins to design their site content. So this feature was added in main plugin. Most of the Visual Composer plugins should work fine with the plugin.