The plugins are the plugouts, if that makes sense. If you want to install Promars on the System1/8, for example, you have to in some way own the Promars plugin. While Promars is open, it will have a button to “plugout” to a connected synth.
So if a cloud subscription gives you access to the plugins, it’s also giving you access to those same plugouts.
There’s a bit more discussion about it over here.