Cubes - Individual faces

I am using a VAO to render a voxel landscape. I am working on some rough optimizations currently and I just had a couple of questions about best practices.

  1. Is it enough to exclude index data or should I get rid of the vertex data too? (it seems faster to just keep the vertex data loaded)
  2. Should I disable drawing by excluding index data or should I use glCullFace(front and back)?
  3. If anybody could point me to some documentation on how to analyze OpenGL efficiencies/run-time, that would be awesome!

Cheers,

-QuicK