Beyond what Chantelle mentioned about removing plugins, some styles pre-load certain Hi-Q instruments. If you don't like using MIDI SuperTracks or Hi-Q instruments, you can always stick with all RealTrack Styles, but if you're working with MIDI Melody or prefer using General MIDI patches that may not be ideal. When you're in the StylePicker however, when you click on a Style, it should show you the instruments it will load at the bottom of the StylePicker, or provide you with a memo box that states info about the style. You can check either of these sections to see if a Hi-Q instrument is going to be loaded. In the memo box it outlines what gets loaded in text, but the instruments listed in the bottom left show the colour of the text. Anything light blue is going to be a MIDI SuperTrack.

Cheers,
Ember