in the material properties, choose the transparency's behavior :
"opaque" means no transparency, that's why you don't have any changes in your viewport even if the shader you have configured is ok.
The "display settings" of the material is in the material panel, while the material itself is in the node editor.
There are 3 alpha modes :
"clip" is a ...
you can add another "mixshader", connect the output of the current "mixshader" to the new.
Afterwards you can connect the "transparent shader" to the top of the new "mixshader".
The factor can be a "color ramp" that is dependent on Z of the object (in fact you can use whatever factor here to control another transparency).
Check the printscreen of the ...
Your nodes are correct, but how can you see through the "walking/thing" layer if your walking/thing render is fully opaque? You need a transparent background for that.
If what's behind your objects is only the world environment, then the simplest way to get transparency is to head over your render tab, Film panel and check the Transparent option:
I figured it out!
The UV maps didn't get combined on join because they did not have the same name. This resulted in all but the first UV map becoming inactive and all but the actively selected mesh, while having the correct material assigned, using that first UV map. That then resulted in the assigned materials then not being mapped properly.