What's the best mod setup for Royal Guard and Geo Soldier?

RG needs tons of health and protection. Since he's a great stunner he also benefits from potency and speed. So get 6 mods with the health set bonus. For primary stats I recommend speed for the arrow mod, protection for the triangular mod and potency for the plus-shaped mod.

GS needs tons of crit chance and speed. Extra crit dmg is nice too. So for the set bonus, you can get 6 crit chance mods. For primary stats you need speed for the arrow mod, crit dmg for the triangular mod and for the plus-shaped mod offense is probably the best choice.