Thought I read somewhere that Barbs only spawn in areas that have been explored but not settler.
Not quite -- Barb-huts can spawn only on
uncovered tiles which are
not currently visible to any (of your) units or towns (i.e. hidden by the 'fog of war'). So by placing a few Warriors on strategic Hills/Mountains around your cities -- or sacrificing Workers/Slaves to build Outposts, in C3C -- you can expand your visibility range quite substantially, and therefore reduce the number of tiles where Barb-huts can spawn.
That said, depending on difficulty level, you might actually
want to keep a few invisible tiles on the map, so that you can 'farm' Barb-villages, because (at least up to Emp, possibly DG) it's easier to get victories/ promotions vs. Barb-units than vs. AICiv-units. That way, your early mil-units can quickly get promoted to Vet without having to build any Barracks first, and/or Elite if they're fast-units (i.e. M≥2). Elite fast-units
apparently have better retreat-odds than Regs and Vets, so getting your Horsemen to Elite increases their survival chances both on attack and defence against M=1 foot-units. If you farm the Barbs, then when it's time to fight the AICivs, you'll more likely have better-trained forces than they do (Raxes do not appear to be priority-builds, at least for non-MIL AICivs), and you'll have more Elite units with which to generate MGLs.
Also, if a Goody-hut is popped by your initial Settler, you will
never get Barb-units from it. For subsequent Settlers, I'm not so sure... I
think you don't get Barb-units if you found a town directly adjacent to a Hut, only gold/ maps/ techs -- but don't quote me on that!