In good midfields you don’t have designated blockers or chasers. Players just read the field and act accordingly to the field that’s laid out before them.
It depends. When you've got Dusty, Petracca, Oliver or Fyfe you can set up around them.
Why you would set up around Parish is beyond me. No where near dangerous or good enough. It's just coming up with reasons to maintain what we have out of sentiment.