[RMMZ] .PNG COLLISION BARRIERS?

Hey, I'm using the Galv plugin in MZ for my maps.

I was wondering if there is a way to use Galvs layers to create s collision barrier with a png?

I'm also having trouble with multiple layers, I can get two static layers to work together but when I try to introduce a 3rd layer, for example: a moving semi transparent texture to create smoke it either takes the place of one of the others layers or refuses to exist.

I'm sure this is really simple stuff, I'm new to plugin so I keep getting the feeling I am missing a very simple part.