The RC cars are 'as built' pre 1938 and too short for the reconditioned 1938-1965 WP cars (unless you use a RC R-30-9 body).
They ride on T-section trucks.
As you mentioned the RC R-30-12-9 cars have Bettendorf frames, which was only the case on maybe 200 of the 2775 WP cars (PFE's R-30-13, which was the basis for the WP cars in 1924, has the built up frame).
The RC cars are missing the bolted on side and end reinforcement strips and coupler pockets.
And the RC cars sometimes have orange feather heralds, which should be B&W.
The RCW kit is 100% appropriate for the reconditioned WP cars that ran during 1938-1965 era and I'm glad RCW offers it now.
It has better details like appropriate trucks, brake wheel and see through hatch latches.
It can be built as a 1938-1941reconditioned WP reefer or as 1952 rebuilt (by PFE, Roseville) version with AB brake and Preco fan + plate and removed hatch platforms.
These lasted until 1965.
Add Tichy decals and silver paint and you can even turn it into a 1951 (WP Sacramento) built painted WP Ice Service reefer which lasted into the early 1970's.
Last but not least a set of Microscale or Speedwitch decals could turn it into a perfect PFE R-30/40-9 car besides the available WP options.