Automapping 1x1 paths (roads/rivers)

I’m trying to use this simple set of tiles to draw 1x1 paths.

First, I tried using the terrain feature. I made the patterns for water tiles as such.

But terrain doesn’t do what I want. I can only draw 3x3 or 2x2, but I can’t draw a 1x1 paths.

Then I tried using rule tiles, but it only works with simple cases, if I start drawing more complex shapes, it breaks.

There is so many possible combinations that the tiles can get into, it doesn’t seem very practical to create rule tiles for all of them. The straights, the curves, the borders, the fillings, all in 4 possible directions. I can’t wrap my head around it.

How can I do what I’m trying to do?

You might want to look at setting up wang tiles, you need a set of 16 tiles to make it work I think.