My guess was that those are mostly year round & not as heavily influenced by tourists. If I’m wrong then that was just my own misunderstanding.
Sparkleberry and North Charleston have a lot more violent crime than the Dyrtle. I just double checked and it looks like the Dyrtle overtook North Charleston, last year. And You're right about tourists bringing in a bunch of violent crime to the beach. MB is has been a transient's town for decades, so it's short term and long term tourists bringing a lot of it in, but the Pee Dee has a bunch of ultraviolent natives, too. Spartanburg is right on 85 between Charlotte and Atlanta, and and North Charleston is right on 26 right up from the harbor, both are major drug routes, so there's violence associated with that trade from transient populations as well, but like you said, there, it's mostly the natives.
There are a bunch of even more violent smaller cities and towns sprinkled throughout the state for even more cultural enrichment. But it's like anywhere else, if you mind your business and don't associate with a bunch of shitbags, the likelihood of you experiencing a violent crime is slim to none.