Hello Litjan,
I have already run a test with SimHeaven completely removed from Custom Scenery plus all the plugins removed from X-Plane and the result was the same (blurry ground textures), so I added them back.
It almost feels like part of the video memory is being reserved for something and not used, and since it's only 6 GB to start with, it has an impact on texture resolution much sooner than it should.
Thank you,
Chip