I have yet to buy the game because hey they manage with their DLCs, but hey at least Yang and Blake (Bumblebee duo) are free DLC.
I'm not familiar with any series besides RWBY, the RWBY you see are the Volume 1 ~ 3 designs.
As for the song in RWBY it depends on which one imo, I enjoy Yang's theme "I Burn" the most, also "Gold" is also good because of it's lyrics (Not sure if it's in the game... I'm guessing it's not)
I mean... the reason why RWBY is popular in Japan and Taiwan, and even to this day is not just it's show alone, but more of its fanbse, and glad that Roosterteeth acknowledges that, they flourish the series via fanarts, AU fanfics and comics. This is why they release RWBY Anthologies recently, comics and artworks from many well known RWBY artists.