Yes, a tarred road all the way between Windhoek and Luderitz (B1 + B4). Yet even for C roads between Kalkrand and Aus you will not need a 4x4 type of car. Be aware that this is one long drive, and if not with 2 drivers, starting right at sunrise, it will be difficult to reach Luderitz before sunset.
We've driven there in a Toyota Corolla without incident. It was part of a longer trip so we broke the journey.
Whilst there we also did a great trip with a local guide down into the Sperrgebiet (you couldn't go by yourself in those days...probably still can't...noy a job for a saloon car). Far quieter, obviously and I think I preferred the deserted houses. Bogenfels Arch was suitably impressive and we had a lovely walk along the beach closer to Luderitz towards sunset with the dolphins surfacing to see what was going on.
Thanks! I'm looking at potentially getting a train now as the drive might be too long...not sure how r get from keetmanshoop to luderitz though!