There are two kinds of VP in the game now. The normal VP condition is met when someone (anyone) controls the required number of VPs, even if for a turn. Several well-timed stealth-attacks could win the game.
In a cumulative VP game, the number of VPs will increase by one for every VP province controlled in midsummer. The more victorypoints one controls, the more points he gets, but even if he loses some of his VPs he might have a chance ofwinning if he is too far ahead. Surprise attacks in early summer can still win the game, but more often it just gives one player an advantage instead of instant win.
As far as starting locations go:
The game does try to give nations spesific starting provinces. I don't think it can recognize desert areas, though, so starting or neighbouring province(s) of the preferred terrain should be enough. Ulm prefers mountains and/or forests, at least, and Pangaea forests, etc. I'm not sure how often the nations start in provinces of their preferred terrain, but I guess it would be pretty often.
The starting sites can be pre-set as well. this is done by editing the .map file (or copying it and editing the copy). Map editing manual in \Dominions 3\doc has details about the process, but it basically consists of one
#specstart <nation nbr> <province
nbr>
line for every nation. Nation numbers are in the end of the map editing manual, not in the mod manual.