with an i7 6700k and a GTX1070 im getting 30-40fps in EDDK on high settings, max settings in EDDK config tool and on a 4K resolution. The only setting which causes my fps to drop to 25 is the Reflection Detail setting set to high. Also make sure that you dont set the Antialiasing on a higher SSAA setting, because for expample 4x SSAA means that XPlane renders internally with four times your screens resolution and then scales it down, which needs a huge amount of memory and overall processing power if you are already above 1080p.
A GTX1070ti however should easily be able to handle that, so im assuming that there is a problem with other Add-Ons or Plugins you use. I strongly suggest to disable those step by step and see if your performance improves. If you do so, please make sure to report back to us so we can fix potential incompatiblities.