Whatever settings you set as default will be saved with your game, so users should experience it as intended.
There are a few options to help speed things up, but it really depends on your PC spec.
Be sparing when dropping trees down. They will slow things if you attack the level with the spray tool. try to use as few as you can get away with. Certain trees may slow things more than others, so try to avoid using those a lot.
If your map does not have water, turn it off using the sliders menu after hitting tab twice. you can also hide it when you are out of range if you do have water in your level. There is a default script for that included with Game Guru.
You can also hide the terrain and water in indoor scenes for extra speed.
For an way to speed up the system with a slow video card you can change the setup file to reduce the texture size value. This will force the textures to a smaller size.
dividetexturesize=1 - change this to a higher number to reduce the texture size.
You can also change the reflection size and such.
There's more but most is covered in the thread mentioned already.
SPECS: Q6600 CPU. Nvidia 660GTX. 8 Gig Memory. Win 7.