Thank you very much for doing a test and even creating the comparison picture!
So, this is of course an art, not an exact science.
It will hugely depend on your content, the lighting, the camera position and so on.
We have noticed, that for some of our content, we can confidently disable masked, after like 20 meters for most of our assets.
That comes with a gigantic performance boost.
I wish there was a way to do this. I’m sure there are other areas, where this added flexibility is beneficial.