#Vertex Buffer Object
Vertex buffering is an OpenGL feature that stores mesh data internally rather than requireing the program to send it across the gl pipeline each time it is drawn. No reason you should have it off unless it causes problems for some bizarre reason (which it won\'t)

#Stencil Threshold
I presume this corresponds to the gl stencil buffer range. It\'s probally just used for shadow projection, higher values may mean more accurate shadows over complex geometry or several overlapping shadows. But I\'m not 100% sure

#Load all maps
Self explanitory I think. Load all the seperate maps @ once @ the start, taking more memory & initial time but should mean no further loading of maps throughout the game

#Stream buffer
Kramy explained it well, it\'s how many seconds to store ahead in advance to avoid jolting (like personal cd player skip protection) But be aware that anything played will lag behind by that amount. a smallish value should be suitable