I just looked back at the opening post and saw this as the last leg of the trip: "Coastal Road to Houston" (from New Orleans).

There is no such road, nor even any such coast, really. Louisiana sort of gradually falls off into the Gulf in a system of swamps or "wetlands." The wetlands themselves are disappearing, too, but that's a whole other topic. (See www.levees.org.) But the main point is that the only practical route is the I-10 intersate highway, which is pretty well inland.

Just as there's no real "down the river" drive to N.O. from points north, there's no "along the coast" scenic route west to Texas. (Now, going east out of New Orleans towards Jacksonville, there are stretches of beachfront driving for those with the time to abandon the interstate for local roads.)

There is a "River Road" on either bank of Mississippi for much of its length, but except for very short local trips, it's not a practical choice. As already noted, the levees are so high that there's absolutely no river view, and the river is so extremely serpentine that you'd have to drive three or four miles (or more!) for every "as-the-crow-flies" mile of your trip.