HI,
yes, the process is ok as you describe it.
Don't send event on each update or several times per update, that would not be good ( even in scripts, it would not). Then you can use broadcast all safely, I have a project with hundreds or Fsm, and global events everywhere, broadcasting to all doesn't have any impact so far, so it will go a long way before any performance hit will be noticeable. Also, always test your scene when published, the Unity editor environment as well as the playmaker editing environment so have serious impacts on perfs, so testing properly publish in its final device or environment is a must to asset the performances.
bye,
Jean