This only deals with several plane markers related to the glitches that you've seen in the images.
More performance-friendly but may not fix other hidden occlusion glitches.
esl-flagged esp. You must activate Only One main file!

Removes all vanilla plane markers in Windhelm to get rid of any potential occlusion glitch you might encounter.
May cause a slight fps drop at certain spots according to your game environment.
ESMified esl. You must activate Only One main file!

This is the .esp lite version.

This is the .esp main version.