Pathes produce excessive geometry.

Screenshot.

You can just turn down geometry detail in settings for patches. If you want control over how a curve will be displayed, you'll have to use misc_model.

That is not really an issue, this is how patches work. You'll see you can change it's detailedness in the graphical settings menu.
Also, DP can render those tris very nicely, it's not a problem.

For the one too-dense patch (in y direction), I'd recommend you to check the uvmapping of the patch. I'd bet that is the problem for it not getting any simpler.

It's one big path with natural texture mapping.