Well now,
Helical...are you shooting through a Bisker whisket? If so, keep them straight. If you use a drop or prong style rest, add as much helical as you want.

A lot of guys use super glue for fletching, but I like to use glue thats made for fletching, such as Bohning fletch-tite, or my favvy Flex bond.

offset just means that one tip of the vane is more to the left or right than say the back.. see pic below...

p.s. I shoot 2" blazers through a WB with straight 1 degree offset to the right. and they stabilize just fine