If you run an Internet search on Vietnam and the war, most of the information you get begins at about 1962. I think this is telling. It is missing the whole period that led up to the reasons the war happened in the first place
It's nice to know that if you've worked really hard at something, it gets recognised with a tick in the success column - however you define that, be it making a bunch of dough, which the actors never see much of, or whether it's a piece that's enlightening or stays with the audience maybe six, seven or even eight or 10 years later.
You can't see any movie nowadays really without it having some sort of CGI treatment, albeit whether it's a creature or an environment, something like that. To make a point, sort of poetically in that case, but clearly it was a drama and how do you approach it? Well, I think what you're supposed to do is what the text dictates. What you bring to it and everything you need to know should be there, and pay attention to your director.
While green-screen work, find a way to stay true to whatever it is that it takes to act a scene out, and make sure that you use your imagination as best as you possibly can, still stay loose, and still allow yourself the liberty of doing what you need to do as an actor, and then work within the confines of what is actually possible.