The hangers that I had them use are fastened into the 2 x 6 fascia board, so the rafter spacing is not important for that type.
My in-laws have the leaf guards and dirt still gets into the gutter on the design they have and needs to be cleaned out. Unfortunately I don't know the mfg of theirs since they were on long before i was in the family.
The type of hangers to be used to support the gutters actually depends on the way the house is finished. In some cases the roof hangers are better than ordinary hangers. Still, have as many as you can of them for max support. Sometimes guttermen use special brackets to make sure the gutters are leveled horizontally.