There needs to be The Guy. Frankly, the 8th and 9th inning should be set. Those guys should know they're not going to be used outside of those innings, or at least, if they are, the coaching staff will tell then before the game.
I think it should go to Edwards, due to being a veteran and having more experience. But I also think Hunter Harvey and Mason Thompson should get some legit shots at closer/setup roles.
Let Harris and Banda grow into being major league relievers in middle relief. Also, no reason to rush Rainey back to high leverage (dont think he'll be here until September anyway).
Rizzo and Davey need to balance the need for development of young, long term guys (Harvey, Banda, Thompson) and maximizing the trade value of short term veterans (Edwards, Finnegan, Ramirez). Ultimately, we should lean to the side of player development.