(In no particular order)

Werewolves
Alpha wolves will always be the largest wolf size at approximately 6'0 at the shoulder, the size of the (extinct) South American Short Faced bear.

Lower tier wolves are much smaller however, standing at around 3'9 at the shoulder, the size of the (extinct) Eurasian Cave Lion.

In human form, while most Alphas tend to hover around the 6'2 - 6'5 mark, other wolves can be any height, similar to humans. Extremes in all classes are possible, as with humans.

Vampires
Any possible height within reasonable human height. Alike to humans in this regard.

Sirens
Changes depending on year siren is born. If born in in a year where taller heights are preferred and seen as more attractive then siren will grow to be taller and vice versa.

Witches
Same as vampires. Any possible height within reasonable human height. Alike to humans in this regard.

Dryads
Dependent on tree species. Taller trees such as redwoods will be taller on the human height scale then smaller trees such as apple or cherry trees and vice versa.

Merfolk
Height is determined by length from tip of tail to head. This length is normally about the same height as the average human.