I've lived half a dozen places between SC and CT for most of the last 57 years, and as everyone says, I-95 sucks almost everywhere. I avoid it like the plague. It's understandable, but unfortunate, that the first coastal SC corridor utilizes it. When driving the CT-VA-SC stretch pretty frequently 15-20 years ago, we would accept an hour longer trip to use I-81, however, there are now many trucks on that road which are slowed by the terrain and traffic load.
The SC buildout will hopefully enable more non-interstate travel for long trips. For the GA-VA stretch, it may be worth going Savannah/Columbia/Burlington/Petersburg when feasible, but the Richmond-DC stretch will probably never have much more option than I-95 and small roads. Fwiw, I routinely ice-drive from Chapel Hill to Columbia on US 15 to avoid the congestion and stress of the interstate routes and Raleigh/Charlotte, and it adds almost nothing to the total trip time.