A 30 pound top shot should be plenty and I’d make it 10 feet or so. That makes it easy for you or a mate to grab and wrap your hands around if you want to hoist in a fish rather then use a net. Rather then a swivel to join the braid to the leader use an Alberto knot
https://youtu.be/aXjagwdjAhg . This knot has a low
profile which passes through the guides better then others and won’t interfere with your casts. If you’re loooking for Flutter spoons Pete at Atlantic Bait and tackle has them in stock.