The KX-155's are not GPS units, therefore they represent the "No-GPS" option.
There is currently no way to load a sequence of RNAV waypoints into the KNS-80 or KNS-81. I haven't looked into it, but I suspect this would not really be possible, given how the flight planning system works in MSFS, as the waypoints are not defined by radial/distance pairs. In theory, I could create a system that selects appropriate radial/distance pairs based on injected GPS waypoints, but I don't think this would satisfy most users who want to follow realistic RNAV procedures, or actual history charts, as much as possible.
Let me know if you have any more questions!