If you are asking about what's needed for playing the Sylphyo, you really don't anything but an amp or headphones. The onboard sound are fully functional and expressive. Much you can do with them. And more on the way.
You could use any number of apps on an iPad or computer, but you'll need to configure the parameters in most to work well with the various CC messages Sylphyo sends out. The onboard sounds just work.
One thing to consider is this: the more sounds/patches you have to choose from, the more time you'll spend choosing patches instead of playing. I can say this from experience and have personally chosen to simplify and concentrate on enjoying playing.