Texture Quality doesn't make too much difference, but using "Balanced Performance" gives a pretty notable boost to framerate, regardless of whether or not you use low/high quality textures. I guess the frame-rate issues were caused by Telltale trying to make the engine give the black ink outlines to more detailed models than in previous games. Using "Balanced Performance" tones down some of the various post processing effects, and the framerate runs as the equivalent of that from older Telltale games. (Older Telltale games from Wolf onwards used the same effects, but I guess it was a combination of the models not being as detailed and other back end changes).
Characters still have the black ink outlines drawn on their clothes/faces/etc, but what I mean is, it tones it down when it came to the game automatically generating it for background objects.
EDIT: To more directly answer your question, they just added lower tiers. As I said, using "Balanced Performance" gives a very consisted framerate. I run on a fairly good machine and would still have the framerate jump in Episode 1, but I had noticed optimization improvements in Episodes 2-4. So, keep in mind Episode 1 is probably an isolated case. However, for more moderate/lower end machines, I imagine "Balanced Performance" will cause a world of difference. if I noticed improvements running on a good machine, than people who had issues running on moderate/low end machines will probably notice a tenfold improvement. I bet New Frontier was delayed to also include these optimizations.
