Hi,
Arturias plug-ins are'nt the fastest out there to load. But it's impossible to say, if yours is loading slower than can be exspected, as you don't tell about your load time and about how fast your computer is.
The DAW can also have an impact on the load time.
It's normal to have the standalone version and at least one VST version installed. Having both VST2 and VST3 plugins installed - and even having other formats installed is normal. This should not affect the load time, unless perhaps a little, if you using a very full mechanical harddisk, so the computer is being slowed down.
You only need to have the Standalone and a single plugin version installed, if you don't need to use more. You can select in the installers, which plugins should be installed.
I'm on Windows. but if you take the time to read the installers text, when you install anything, then i think you actually should be able to answer the path questions you ask yourself.
I guess that you - like i - can look in Arturia Software Center (ASC) prefereces under folders to see where the VST versions is installed on your system. It sound like you have installed on default paths.