I have a splash plate and ground plate but will they work on pokemon like floatzel and garchomp?
All the plates boost moves of the same type by 20%
Ex: If Garchomp holds the Flame Plate and uses Fire Blast, the power will be boosted by 20%.
As UberPwnage said, all plates raise moves of the same type bye 20%. The only reason arceus can change its type and color is because it has the ability called multitype, which other pokemon cant get.