GameName
The GameName value affects the save location of your server. This will be the name of your save folder. Interestingly enough, this value also affects decoration placing in your server. Trees and other entities for example. It does not affect the layout or topology of the map. An example is shown below:
<property name="GameName" value="MyPerfectWorld"/>
GameDifficulty
This is a number from 0 to 5 indicating 6 levels of hardness. Zero is easiest, 5 is the most challening difficulty. A simple example is shown below:
<property name="GameDifficulty" value="5"/>
GameMode
The GameMode option allows you to switch between GameModeSurvival and GameModeSurvivalMP. Simply enough, MP allows for building protection in a multiplayer environment. A final example is shown below:
<property name="GameMode" value="GameModeSurvival"/>