6 terrains and 2 figures is anything but a simple scene. What's the poly count at the bottom right of the interface?

What is slow? openGL display, or rendering? And what version of Vue are you using?

If it's the openGL, lower the display settings, under the preferences menu, even go for wireframe. If you use Infinite, you can use wireframe for orthographic views, and keep openGL for perspective view.

If it's rendering, what are your render settings? Often, GI quality can be set to -1 without quality loss.