AKKA.NET Architecture Best practices

Question

I'm writing (going to write) a distributed cluster apps using AKKA.NET, but i still have some unclear points:

1. It's better to add all actors in one app (exe file) and running it in one win/linux service, or it's better to create many apps containig one (or few) actor and running them in many win/linux services?
2. What is the best practice to scale a cluster adding new actors, plugin?
3. What is the best practice to handle HA/FT? Run many nodes with the same actors?
4. If I have two nodes with exaclty the same actors, and actors receive/handle the same message, how avoid duplicated actions?

Thanks