It depends on what full package means. QGIS standalone comes with all dependencies required to work properly with its functions available on that version. QGIS standalone installer has a small file size because other functions (plugins) can be downloaded from inside QGIS when you need them. It is different from other commercial software, such as ArcGIS, that you install everything onetime including the extensions, then you just activate the software and extension based on license level.
If you need more advanced installation, you can download OSGeo4W installer, in which you can select QGIS, GRASS, and SAGA, and any additional software. But you will notice when you download OSGeo4W installer that it has also small file size, because it downloads everything from inside the installer. In this case, it is recommended to be connected to the internet, and I think in your case it will take long time because the internet is slow.
If the plugins were downloaded from the Plugin manager, it will be difficult to save them on a separate folder later. So the best way to keep the plugins on a separate folder is to download them separately from QGIS Python Plugins Repository. Then extract the plugin to
C:\users\<username>\.qgis2\python\plugins. For example, if you want to download Profile tool plugin:
- Select the plugin that you want, and click on details
- Go to Latest stable version:
- Click on Download.
- The size of profiletool-3.7.1.zip that was downloaded is just
33kb. You can keep the downloaded plugins on a separate external folder to use them later.
The downside of this method that you need to update the plugins manually following the same process. But from the Plugin manager inside QGIS, you just receive a notice of which plugins need to be updated and they can be updated easily.
The size of the downloaded plugins are very small from kilobytes to megabyte depending on the number of plugins you download.