Yeah, the English version of CLIP STUDIO has a stripped down interface, but some of the features still run when you start it. It looks like you have an account, so it is most likely syncing the material you installed locally to the cloud. This is not something you can disable until they finally embrace this useful software and open up more of the menu items.
With this stripped down version, you cannot easily check what is installed. But if you click the gear icon (settings) > "Location of Materials" you can see the path where they download to. You can also change that path to another directory if you want, as long as it doesn't contain folders called material and documents, and it's not located on removable media.
You can actually check in the material folder to see material that are installed, but with how they organize it folder-wise, it can get confusing fast.