It's not so much that is matters which is the wife and which is the girlfriend, but it does make a bit of a difference. I missed the first episode. Watching the second episode, I was thinking the blond was the wife, and I was thinking "fucking unicorn hunters..." then I remembered at the beginning the brunette said she was the wife, and I thought "Oh... I'm confused now."
As I said, I missed the first episode, but I'm liking the show. No, I don't think it's a "typical example of what polyamory is," or that "it's a good portrayal of polyamory." It is what it is. I doubt a typical example of polyamory is a real thing that exists anyway. The show is supposed to be entertainment, not poly propaganda. Viewing it as such will lead to disappointment. Perhaps it could be portrayed better, but it could be portrayed as much worse. "It's not a terrible depiction" would probably be the best way to put it.