How do I remove Moire patterns from defishing?

[Selur]

Vapoursynth preview error: Validation failed: !params->renderable || fmt_caps & PL_FMT_CAP_RENDERABLE (../../../../../src_packages/libplacebo/src/gpu.c:234)  for texture: ../../../../../src_packages/vs-placebo/src/shader.c:122

Seems like for some reason GLSL filtering doesn't work for you.

As far as reducing to 2K, my video editing strategy is to crop my 4Ks to size and position of interest

So you end up with 2K content that is like some badly upscaled SD.
Assuming your raw footage from the camera has more details, you might want to look into your workflow, this lack of detail 4k is not normal.

Using 10 bit 264,...

10bit helps with banding and offers better compression/quality ratios.