Apologies if this isn't the appropriate forum…

I'm drawing a city map in isometric projection in Photoshop. I'm something of a novice and am using a wacom tablet. My aim was for something along the lines of the Renaissance age city maps, John Speed, Georg Braun, Civitates Orbis Terrarum, but what I'm getting is a bit too regular, almost circuit boardy for what I'm looking for.

Using an isometric grid has been great for me, as I'm not a good drawer, but I was hoping to get some tips for how, with the basic layout done using the grid, I can alter it more toward those styles I've mentioned.

How do people approach drawing maps in those styles? Are there any resources people can point me to that will help?