I thought the same about the NX vs the equivalent RAV4 but checked it out anyway, the Lexus definitely felt another level despite same running gear, don't know RZ compares to the NX but the NX was a far nicer place to be than the Toyota i'd pay the extra for Lexus.
I'd image the RZ would match or be superior to that, same with the comparison to any Kia, Kia are a lower quality product IMO or at least feel that way even if the running gear might be superior.
Spec sheets don't tell you the whole story, things like fit and finish and ride quality also matter.
Fast charging speed of the Kia sounds great but the ability to use that level is about as convenient as filling a Hydrogen car
I am lucky enough to have a 150Kw station that's just opened down the road though, which will help should we have a charging fail.
In my car replacement journey, the Lexus dealership experience in Bristol trumped every other brand, it was only that the car didn't quite fit us we're not in one.