Unless they pull something out of left field Loki S2 is going to be about 500 times more important to watch that Brave New World. I can't imagine how BNW is relevant at all. The only thing it really introduces to the MCU that might be important is Adamantium and I'm 90% sure they mentioned that in the trailers. And even then if you're watching the old X Men movies you know what that is. And if you don't know a wiki article with be a better use of your time.