Looks like they've continued that in their new sets. On the X850B, neutral sharpness is around 35/100. Anything below that, and it actually starts to blur the image (seriously).

I think a good policy is to try to find source material (ie. paused frames) that demonstrates what each enhancement feature does. Anything that removes, smoothes or blurs detail should be disabled. Anything that adjusts black levels, contrast, color or tint in a way that significantly alters the image from a reasonable baseline, should be disabled.

Sometimes, there are settings that at perfectly fine to leave enabled on a low setting - a number of the upscaling-related sharpness settings on the X850B are that way, and if you don't leave Advanced Contrast Enhancer on at least low, you lose frame dimming entirely. There's a setting on my Kuro that if you turn off completely, the picture becomes a blurry mess.