In Vibrant Visuals, the fog in the pale garden is not dark as like in the previous preview and the fog in the desert and mesa is not as warm as it is before. The same happens in cold biomes in which the fog is not in a blue tone. For some biomes it is looking ok like in swamp and jungle. I don’t know if this was an intentional change as there are no mentions about this in the changelog of the preview 1.21.100.20. You can see this in the images given below.
This issue is being tracked at MCPE-221686.