Quick question: If I put all human players in the same force, but set all human players to be enemies of each other, will the bring trigger recognize those other human players as 'Foes'?

Yes, Foes is anyone that is not your ally, if they are not allied to you, but you are allied to them, it does not count them as a foe. But if you are enemy to them, they are a foe.

And whats difference between foes and non-allied victory-players?

There is the option to have Allied Victory on and off(That little check box at the bottom) there is a difference between allied victory and allied.

lol, wanted to ask that. Thanks a lot, Falkoner!