We are here discussing things on a very high, sometime theoretic level. Until 1916 there exist light ammunition support unit at the field-artillery and foot-artillery which were part of the artillery regiments. After 1916 all support units were separated. Foot-Artillery units of the "Garde" were wearing Swedish cuffs, the other units of the field artillery (you are right) Brandenburg cuffs. And I think the dragons have K98 guns and not the "Gewehr 91"
So please again, can you tell me your sources?