What are the differences between

What are the differences between
mountain moss
yamagoke moss and
sphagnum moss ??

This is a good example of trying to be specific about generic terminology.
As i understand it the terms Yamagoke Moss and Mountain Moss are general terms used interchangeably. They typically grow in forested mountain areas. Neither term indicates a specific type of moss but rather a group of moss types collected or propagated.

Sphagnum Moss grows in flood lands and the decayed form is sold as peat moss. Once again there are different specific types of sphagnum moss.

Easy to be confused as the retailers and manufacturers rarely state the specific genus and species of the moss contained in their products.

I use live mountain moss’s for display purposes and shredded sphagnum for top dressing. The mountain moss’s are selected on colour variation and clump shape. With sphagnum the difficulty i have is finding good quality sphagnum on a regular basis!
Perhaps others can fill out with further more specific information.

Yamagoke (“yama” = mountain, “goke” or “koke” = moss) is a popular top dressing for azaleas because the moss particles lock together well and don’t lose their shape when they dry out.

White sphagnum moss, also known as New Zealand moss or orchid moss, is a popular top dressing for many species. It can be used straight out of the bag (after moistening) or shredded when a thinner layer is desired.

Green sphagnum moss isn’t a popular choice for bonsai as constant moisture is more likely to encourage it to start growing.