Hi Rikki
VSTs come in 3 main types, Dedicated Instruments, Large Sample Sets and Effects, all of which require their own CPU power and Ram, the Art is to configure what Instruments and sounds you require for a song(s) in such a way that the computer system does not fall over. (Depending on the computer system and VSTs used, you may need a different configuration for each song)
This is the steep learning curve I mentioned.
I hope to post about VST use and Wersi on my web site when I have the time, the main advantage being that as Wersi have full control of the interface, VSTs become almost as easy to use as just loading in another sound.
Hope this helps

Bill