For run-time performance (not exports) improvements, you can try adjusting the following parameters:
- In the Layers tab - Use a lower working resolution.
- In the Display tab - lower Shadow Resolution, lower GPU Tessellation, and un-check Backfaces, and Anti Aliasing
- In the Performance tab - turn off High Quality Blur, Enable Downsample Textures, Lower Normal Matching, enable Bake Layers and Fast Paint Preview.
For improving performance when exporting, lowering the resolution is currently the only remedy.