3D plot - no, not that I've seen and I think I've turned over every stone. The closest is here, where someone used noise sensors mounted on the bow and measured noise duration at a smaller range of brace heights in 2mm increments and picked a value, then did the same thing with a bunch of tiller values at one brace height and picked a value, then repeated the process with brace height at the new tiller value. Unfortunately, even with 10 shots at each setting the data is so noisy that a large number of the brace height and tiller values could be chosen as the "minimum", and there must have been changes in experimental setup between the graphs as the noise for the loudest shot at the "ideal" brace height is less than the noise for the quietest shot in the second graph despite brace and tiller being identical to the first.The short answer is I don't know. People talk about tiller/brace height being 'personal to your particular set up' i.e. that includes how you shoot.
The comment was more aimed at the people who have a very distinct 'best brace height' as a polite way of saying that you might want to look at your tiller choice.
I think the 3D plot is really interesting! Has it been done before?
You could use it to choose some different bow settings and then see if you get better groups. When you can shoot again of course.
My plan is to pick a few points of interest in the 3d plot (any local minima and maxima in noise) and see if the grouping is different. Unfortunately it takes me a lot of arrows to notice a difference, unless the difference is at the level of group size changing to meters or mm.