Scala paired with Akka is definitely good for that, I don't know how it compares performance wise with Elixir, would be interested to know. We're building a game server backend with lots of messaging in Akka.
However, the BEAM is not very fast on executing actual code, it is like Python in that way where it is good to slave out CPU-heavy work; the BEAM is built for async IO, and yes, running a JVM (or C++) system as a node on a BEAM mesh is fantastic for that (or a port, or NIF for small work).