I'm not aware of any state laws re: hooks per rig. There are often tournament-specific rules if you're fishing competitively, and there may be some lake-specific rules (none that I know in my area) in some places.
I typically use swimbaits loaded up on 1/8 ounce jig heads in whatever favorite color (I use white or shad patterns); either standard paddle-tail swimbaits work, or some use curly tail grubs instead. I have seen them trolled a lot, especially for stripers, but I am always after largemouth and typically don't troll so when I have used one I have been casting. Buddy of mine has more time with it than I do, and I have seen him catch some nice fish casting a Flash Mob Jr. If you're casting one, you'll need a stout rod, preferably a long one, and heavy line. The tension on the line when you cast it gets pretty high, hence the bigger line requirement. It's more of a strong lob than a cast, really. Lately I have been using a heavy action 7 footer with a baitcaster loaded with 50lb braid - this was the setup I had for fishing milfoil mats in Alabama recently, and it turned out to work nicely for my A-rig after I got home.
I have no experience using it for salt species, but I can say that I have worn out some specks with a white money minnow swimbait when I go to Pensacola, so I don't see any reason that an A-rig wouldn't work.