I have a few thousand images to batch process and using the GUI it is almost impossible. The more images you add to the queue the slower it gets to the point it is unrealistic to process anything.
I did a test - I added different number of images (720 x 480) jpeg to the queue and in the settings only enabled Denoise to all images (all other settings disabled), saved output as JPEG Quality 100.
Closed all images between runs
To process 10 images it took about 5 sec or 0.5 sec / image
To process 100 it took 73 sec or 0.73 sec / image
With 1000 images it took 2897 sec or 2.897 sec / image
As you see, the bigger the batch size, the longer it takes to process individual images. There is definitely something wrong with the application code here. It is probably doing something inefficient involving all files in the batch such as enumerating all files every single time you process a single file or something like that.
Topaz Photo AI [v1.2.4] on [Windows 11 x64 with 32 GB RAM]
GPU processing using NVIDIA RTX 2060 Super
EDIT: I compared with Denoise AI v3.7.2 and it absolutely kills Photo AI in terms of speed. I added the same 1000 test images to the queue and it zipped right through them completing them all in 5 min 21 sec = 321 sec = 0.321 sec / image. Wow. There was no noticeable difference in speed per image when changing the number of images in the queue.