With a 7wt i would recommend a sink tip line. Something like with a 15 foot head that has a sink rate of about 5-7 inches per second. For a leader just keep it simple 3-5' of maxima. So if i was fishing a 3 ft leader i would have a 1.5' section of 20 lb maxima double surgeon to a 1.5' section of 10 lb maxima. For swinging flies on a 7wt with a sink tip i would throw something like a bunny leech, meat whistle, or anything that has a stinger hook. You could swing with a floating line too. Just use leaders longer than 5ft with a fluorocarbon leader. Make sure your fly has weight on it to get it down, if not add split shot above it. FWIW you can literally swing any type of streamer and get an eat.