I am planning on a driving tour of Namibia, hitting some of the highlights. To be specific: Windhoek to Etosha to Swakopmund/Walvis Bay to Sossusvlei, and then back to Windhoek.

I have 3 following questions I hope this thread can help me with:
1) For such a trip, is a 4x4 vehicle a must or optional?
2) From Etosha to Swakopmund, I was thinking about either C39 down to Skeleton Coast NP or C35, which is certainly faster. Do you have any opinions on which route is more interesting to see?
3) Any accommodation recommendations at Sossusvlei?

Thank you all.