Silver:
On all the GNS approaches I have done (practice VFR approaches for training), the approach is a pseudo non-precision, and not an ILS replacement. The idea is to facilitate difficult approches in high terrain. So many of them bring you in with a large approach offset, terminating in a decision of about 1,000 ft or so.
There cannot be any offset in an RNP AR approach that has RF legs. The final roll out point (FROP) must be aligned with the runway centerline.
If you have a 3 nm missed approach point, there is not much point in having lateral accuracy much greater than 0.3nm. The approaches are nice, down the valleys etc. But there are gotchas, like where do you go if the FMC loses the curving path half way down.
If the approach value is less than 0.3 and/or the missed approach is less than 1.0, then you must have independent position information that provides sufficiently accurate position information for extraction (typically one or more IRU). It's called extraction because you may get "unable RNP" well prior to the MAP.
"Dual string" is the term the avionics engineers use. The VNKT approach is dual string because of the missed approach requirements.