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?

Thanks!