[Klaus]

I have got a Macbook Pro 15 i7 from 2017 here.

A 42mp Sony file takes about a minute when using the GPU (Radeon Pro 555). With the CPU only it takes about 5min ...
When it comes to AI/machine learning, it's about the GPU or specialized chips. The CPU is just too slow.

So yes, you will need a powerful (supported) GPU. A current gen Macbook Pro 16 will be about twice as fast (30sec).
A high-end gaming GPU, should do it in sub-10secs I reckon.

My Radeon Pro 555 (42mp->1min) has a passmark of about 3140.
If you know your graphics card - search it here: https://www.videocardbenchmark.net/gpu_list.php - to look up its passmark.
The ratio between them can give you an idea of how fast your machine is.
The best GPUs have passmarks of 20000+.

FWIW, I've just tried an ISO 12800 file - while it looks a little plasticky, there's a lot of detail in the image. If someone told me that the image was taken at ISO 200, I would believe him. However, I reckon the result depends on the specific subject - and it can't really restore dynamic range.