I keep it simple, and try to use a gun that is choked for what I expect to see while hunting, if I expect mostly close shooting, I like a IC/M choked gun, if distant shooting M/F. That said, sometimes the birds don't agree with my expectations and instead of close tight cover shots, all I get is long open field shots all day.
Turkeys are about the only bird where I know F/F will work just fine.
Blind hunting ducks over the stool, I really like a LM/IM setup if I'm using steel. Used that for years out of a Citori with good results.