@Thorsten, thank you for your feedback. Pardon my ignorance, but how do I change texturing scheme to improve performance?
The performance depends on the mesh density, not usually on texturing. Despite a few claims to the contrary, textures only influence your rendering performance when you managed to exhaust GPU memory with them. But in general textures are a small factor compared with mesh vertex data.
You can change to 'global' or 'dds' in the rendering dialog, and this will give you different visuals (in most places inferior as they're not region-specific), but the performance difference is so small I've never been able to measure it.