Yes, the order matters: plugins are bound to the compiler and applied in the order specified. You can look into webpack/tapable for a clearer idea on how this works.
Usually, though, you are not forced to think about ordering when binding compiler and compilation plugins, as plugin authors expose specific events that help you reason when your handlers will be invoked.
webpack is not a task runner.
These plugins are tasks, which is not "webpack-style" and not supported. You can report the issue there, but there is nothing to do on webpack side (and I don't care much).
-sokra