I think I kinda sorta figured it out ... Size on all is the same. WR , WR II and WR II X are listed slightly larger only because of their different "extended" frame design. The Windrider II is the original design PC 20 poly with verticals connector making them stick over the LE. The Windrider II X is the same kite merely with PC 31 poly used. Now the Windrider III is a new frame design with PC 31 poly and new frame connectors keeping the verticals below the LE and the verticals cap knots inside a pocket. I assume the sail on all of them is identical.
For a full sail WR III at 189 for kite only this is in line with the OKUSA Vertigo, but not better. However for the many vented options and the UL at the same price these WR III are a deal if they are well made and designed to fly well.
Emma kite also shows a nice chart of vent and frame options (see below) that exactly shows where in the frame the T1 T2 or T3 rods are used on each model.