It's just how it is. The consumer PC isn't gonna cut it even if you're using 4090 plus the best CPU, this is because the typical gaming PC is more tailored for gaming than work. Unless you can afford a monster using a mobo that can support a threadripper or 2 CPUs, a ton of RAM, plus a few or even a dozen GPUs(last I checked they use Quadro, that was years ago, not sure what's best now), you are not getting the speed you want. And that work PC is not going to be good for gaming.
I convert a portion of the vid that I want to watch, it's quite insane to convert the entire vid, I wouldn't be surprised if it takes over 2-3TB for a 8k title.
There are some settings in Topaz you could play around, might help a bit, but don't expect anything noticeable.