Nighthawk X6 AC3200 Tri-Band WiFi Router to NETGEAR - Orbi AX4200 Tri-Band Mesh Wi-Fi 6 System (2-pa

As FURRYe38 pointed out, WiFi and cell phone service are entirely separate. (different radio frequencies. different technologies. etc.) Nothing you do with regard to the WiFi network will have any impact on cell phone service.  That being said, some smartphones are able to use WiFi for calling (and maybe SMS text?).  (I am constantly frustrated that my own smartphone does not feature WiFi calling, but I am too cheap to buy a new phone just to get that feature.)  If by "cell phone" you mean "WiFi calling", then the WiFi system may matter.

There is a world of difference between the Nighhawk X6 and Orbi 'mesh' WiFi.

• The Nighthawk X6 is a 'tri-band' router and creates two separate 5G WiFi networks. There is some 'magic' internal to the router to steer devices to one band or the other.See page 74 of the user manual:
  https://www.downloads.netgear.com/files/GDC/R8000/R8000_UM_EN.pdf 
• The Orbi is also a 'tri-band' system but uses only one 5G band to talk to user devices and uses the other 5G band to talk between the Orbi router and Orbi satellites.  Having no satellites, the X6 is able to create more bandwidth for user devices.  (Realize of course that no matter how much bandwith user devices have on WiFi, they are limited by the ISP internet connection.  What is the benefit of having 2,600mb of capacity internally when the ISP is delivering 200mb? (or 400mb?)
• The X6 allows users to connect an inexpensive USB hard drive as Readyshare storage. Orbi does not support USB hard drives.
  (My guess is that few customers actually make use of this feature, but if you do please be aware that the Orbi does not support it.)

It is not clear what the concern is about the barn (cell phone service or WiFi coverage).  (again my guess is) the concern is WiFi coverage in the barn.  100' is considered 'far' in WiFi terms.  Some users have reported coverage that far. Most have not. The forum has many posts regarding extending WiFi coverage to outbuildings. (search the forum for 'barn').  A typical Orbi system is not likely to be a good solution by itself for this problem. (Nor is any other vendor's 'mesh WiFi system'.)

Sorry to remble on.  Once I get started.....