That's a delightful painterly style. About the only thing that looks awry is that some of the rivers are TOO obviously just drawn across pre-painted terrain. The strongest impression of this is that spot in the northern mountains where the river's path seems to run over the edge of a mountain. All in all, though, very nicely done!

I don't know about workflow you might like better for city generation, but as a general thought, to stay compatible, maybe a compatible style would be looser painted suggestion rather than detailed precision. Or maybe if you need SOME degree of detail, using intentionally sketchy / handdrawn linework would work. You do realize, that in order to suggest better city methods, you're going to have to show us the present methods you don't like? Don't fret - with an intro like the NW Anthemios map, we won't think poorly of your cartography.