I just sent you a PM. As for environmental design, it really depends on the kind of project you are working on. For the most part, it doesn't have to be a playable map, your job is to take a basic looking map and turn it into something filled with awesome art. EDIT: Whoops, missed the second question. Source in my opinion…
They are related positions, the difference is that the level designer focuses on making a level gameplay ready, or in other words "fun" whereas the environmental designer focuses on making a level "pretty." You shouldn't worry about which tools to use because at the end of the day, they're just that, tools. A carpenter…