Last time I looked at Elixir, it seemed like the consensus was "you're going to need to do Erlang too". Is that still the case, or is dipping down into Erlang no longer required?
If you have decent familiarity with Elixir, understanding Erlang isn't very difficult. You spend 20 minutes grokking the slightly weird syntax and then it's generally just a subset of Elixir. This is of course a bit of a simplification, but it's close enough for when you're trying to understand someone's Erlang code.
For sets it's usually recommended to use Elixir MapSet. There is a Queue-wrapper around the FIFO-queue in OTP as well. For fun and learning you can also implement your own queues, or things like process pooling around the tooling already available.