What is the correlation between "No Weight-Blend" layers and the "Alpha Blend" blend type?


When you create a Landscape Layer you got the option between a “Weighted(normal)” Layer and a “No Weight-Blend” layer.

When you use a Landscape “Layer Blend” node in the material graph you can choose between 3 blend modes: Alpha Blend/ Weight Blend/ Height Blend.

I wanted to ask,

First: what is the correlation between these 2 layers types and the 3 Blend Types?

Second: Must I use “No Weight-Blend” layers only when I want to use a “Alpha Blend” blend mode?
In the documentation it is advised that the first layer in a “Layer Blend” node should have the blend type “Alpha Blend” to avoid black patches in certain portions of the landscape. Should this layer also be set to “No Weight-Blend”?

Third: On the documentation it is also advised to use “No Weight-Blend” for layers like “Snow” and “Puddles” who are supposed to be on top of the blended material stacks no matter what. Does that mean that if I want a Snow layer I should use “Alpha Blend” blend mode in conjunction with a “No Weight-Blend” layer?

Fourth: If, in a material which has already a stack of layers blended together with a Layer Blend node, I intend to add a layer with the unique purpose to be used in conjunction of a landscape Layer Sample node, rather then be added to the Layer Blend node, should this new layer be created as a “No Weight-Blend” layer? (For instance to create a “Puddle” mask where I will use this mask to multiply some roughness and specular with a certain value).