The performance claims for what? I have seen it in person for RIS and it was 1-2fps. I have also seen reshade filter generally and they can take anywhere from 5 to 10 fps depending on the image.
Indeed, not sure what people about upscaling are talking about though. Everything I have had suggested there wasn't anything in that regards.
The confusion about upscaling is coming from the fact within Radeon settings GPU upscale must be enabled for RIS to work.
So when you run 1800p on a 4K monitor the GPU upscale the image to that display then RIS kicks in before the upscaling not after giving a better image.
This is the key steps about RIS is sharpening the image before the upscaling.