While I have not run non-official settings besides homebrew (I love Greyhawk too much), I have played in a couple. I'm currently in Primeval Thule, which has a very Conan the Barbarian, Sword and Sorcery feel (plus it's already adapated to 5e). Another good one was in 3E (who's name I cannot recall nor find) had a world where there were nine gods (one for each alignment) and a blood sea (which was polluted with the blood of a slain titan) that was a very good dark fantasy alternative. I wish I could find that one again.