Water droplet clouds, lower and medium levels, are the cause of overwhelmingly the most of the 'greenhouse effect' (CO2, methane, etc. are tiny by comparison).
British Geological survey
Water vapour, as a gas, not droplet, has the greatest contribution to the 'greenhouse effect' and it is present throughout the whole depth of the atmosphere.
As an illustration of the relative importance of clouds compared to gasses in the terrestrial energy balance :
Note clear sky emissions to surface compared to {319}compared to cloud {26.6}