Frieza has 3 established levels
The Dragon Ball expanded universe, and video games, establish Mecha Frieza as being weaker then the third transformation he fought Goku with on Namek. Frieza himself stated that he had not been so challenged since fighting his own father while fighting SSJ Goku, he also stated Goku never fought his "Final Form" which many speculate means Frieza could transform into the same top level as Cooler could in Cooler's Revenge.
Considering King Cold is unestablished in power we cant make a judgement on him, the form Frieza said he was challenged by is debatable, Trunks beat both with ease.
Cooler has Five forms. He stated he was stronger then his brother or father
Base (never shown due to maintaining a more peak form)
Second form (never shown due to maintaining a more peak form)
third transformation was Cooler's default
fourth transformation Stronger then Frieza
Metal Cooler is widely established as the strongest incarnation of the three villains