Go play have fun. The only places you don't want to fully delve into are far north and far south. As soon as you see it appear on the map just stop going further. But honestly go for a little wander if you like you'll be exploring like 1 hundredth of an area, I doubt very much it will break your game if that little patch is walked on.

I explored heaps of mistlands pre mistlands and the map is still completely usable , and I've got a nice big patch of Ashlands and deep north explored, is fine