As @victorbjorklund says, it depends on what you are after. Elixir performance characteristics are pretty well documented in these forums. Examples include:
Elixir is not great at heavy duty number-crunching (although, depending on what you are doing, Elixir-Nx is addressing that).
However, for things like web-apps, the templating system and process model make for very efficient, performant web-apps that stay predictably responsive under load - e.g. no “stop-the-world” garbage collection.
“Blockchain apps” is a very broad set of possible applications with wildly different performance requirements so I don’t think you’re going to get a better answer without being more specific.
