I have the X-T2 with 2 cards LEXAR UHS-II 2000x. One is 64Gb in slot 1 for lossless compressed RAW, the other is 32Gb in slot 2 for JPEGs.
Coming from an X-E2, this is another world....
After filling the buffer at 11fps (after 3/4 seconds), the buffer is quickly emptied.
I've read before the launch that shooting at 5fps with this configuration (UHS-II cards, compressed raw on one card and JPEG on the other) give an endless buffer... and this is true, I was not able to fill the buffer (but maybe after 1 minute of shooting....)
I may post a video of the performances if you really need one ;-)