Paul might show up to try and gather than rural libertarians to place 2nd if it is proportional. He might get 2 or 3 10+ delegates. His chance of breaking 20% here is better than breaking 10% in SC, so he might as well try (it would probably require he wins one of the first two or is at least a very close 2nd possibly both times).
The delegates will be awarded on a quasi-proportional basis, but the number of delegates we're talking about is trivial compared to what will be awarded on Super Tuesday. At that stage in the game, it's all about doing what you can to produce momentum for Super Tuesday. In which case, it's unclear that there's much of anything to be gained by finishing such a distant second in Nevada, when you can spend your time trying to break into the top three (or higher) in South Carolina.
Is it actually easier for Paul to break 20% in Nevada than 10% in South Carolina? I don't know. Rand is not his father. It depends on how he campaigns, but it isn't obvious to me that he's doomed to such poor showings in the South.