I have the option on my A6 ECE projectors where i can either have a Z cutoff or i can switch both to a straight cutoff.

I'm just curious, what would be the difference between the two?

Please read this whole string:
http://www.network54.com/Hide/Forum/thread?forumid=216460&messageid=1067074951&lp=1067201425

The flat cutoff is for European countries that drive on the right lane of the road, but are visiting UK (where they drive in the left lane), and when you are over the border in UK you don't want the top RH flare in your beam to bother oncoming traffic. But if your in any country that drives in the right lane then you definitely want the Z-beam or you'll severely sacrifice your far distance night vision

well i don't have the upper shield like his projectors.

Upper shield does not form any part of the cutoff line.
Upper shield function is described in detail on the bottom of this page: http://faq.auto.light.tripod.com/projector-unit.htm