The wire sizes were all appropriate for 12 which means they would work for 24. I'd be very surprised if anyone is building a 24v Rv-14, but the wiring will work.
If you're contemplating building a 24v RV-14, I'd be curious to know why. My guess is that with so little weight savings in downsizing the wiring for 24v the battery needs would raise the weight. I haven't really thought about it however, seems like a lot of complications at first blush.