From the 4 Hobies I've owned, I've done my fair share of tangling, er I mean trolling
Whether it's livebait slow trolling or dragging artificial lures, IMO 2 is the limit if you ever intend to turn or if you're aiming for fish that might fight in circles like King Mackerel or Mahi Mahi.
Otherwise you should be able to get away with trolling one diving plug and one surface lure (like a feather lure), as long as the surface lure is farther back than the diving lure so it will pass over the diving plug when you make GENTLE turns.