I always see layers that are colored on , put UNDERNEATH the lineart layer in tutorials... but when I put layers underneath the lineart layers.... the color doesn't show up.... Am I doing something wrong ?
Preserve opacity : it locks the layer, anything you draw on the layer won't go out of the edges
Clipping group : similar to preserve opacity, but on a different layer. Anything you draw on the new layer won't come out of edges.
selection source : I don't really use it. But you can set your lineart layer to "Selection source", instead of selecting to color the base colors, you can make a new layer, with setting the bucket target to "Selection source", and then just fill in without the need for selection
I dunno if you understand me , but you probably would get it when you try it