Dried and cured hemp will absorb liquids, so they do filter some oil. The material isn't as porous as paper though, so it won't absorb as much as paper. Consider it in between metal and paper in this regard. Also, the absorption properties of hemp will degrade with saturation. This is true for paper filters too, but since hemp are reusable, remember to wash them with soap that removes oil (like Dawn) regularly. More often when brewing dark roasts and extra often with extra oily dark roasts.

No

At least not in general. The pores in hemp filters are not as fine as in paper filters and will let through some oils. While undoubtedly it reduces the amount of oils a lot, it is not as good in filtering coffee as paper filters.

However, evidence that unfiltered coffee raises cholesterol levels significantly is questionable at best. Filtering it with hemp will certainly help, filtering it with paper filters will help even more.