I am not with Laminar Research or any other company mentioned below.
Stay with the Intel processor rather than the AMD processor. The Intel CPU is known to provide a better performance within X-Plane. The situation is known to reverse when used in different situations or software packages. There are several YouTube videos that are available for reference. If you plan to overclock the Intel processor you need the i7 8700K cpu rather than the i7 8700 unit. The "K" designation indicates the processor can be overclocked. Also to assist in the overclocking make sure you have a "Z" series motherboard eg z370 rather than something else with the designation using another alphabet letter.
In relation to the graphics card the NVidia GTX 1070 card does work quite well. It is supplied in top-of-range PCs built by XForcePC within the USA. This company is recommended by Laminar Research as the preferred X-Plane PC builder within the USA.
The NVidia 2080 is the next generation graphics card recently released. From Information seen it has a better performance than the GTX 1070 card and is supposedly equal to the previous 1080ti card. Have a look at some of the videos made by Michael Brown at the following link at https://www.youtube.com/user/col2mab/videos
Michael owns XForcePC.