I’ve patched the next GTK theme for Gnome, for a screen resolution of 1366 x 768 pixels. The changes include reducing the CSD height, changing the padding on some buttons and decreasing Gnome Terminal tabs height.
There are still some bugs with the theme. For example, Eye of Gnome still has a huge CSD height. I’ll hopefully fix this in the near future, if doable via theming.
Feel free to clone it or fork it.