Hey fabio81,
Do not use the AI denoiser for final frames :) It isn't meant for that, it has no temporal coherence and it does a "rougher" job cleaning up the image than the high quality denoiser. Don't think the HQ has TC either but it does a more precise job at preserving edges and details.
I suggest rendering to about 5-6% and denoising at 0.5 . I think those numbers worked good for me in most cases.
To quote the helpdesk - Fast Preview Denoising should be used mostly for interactive rendering, quick previews, and optionally for final stills (High Quality Denoising is designed to be used for high quality stills and animations)
I also totally agree with Tom, obviously the random sampling will look horrible when you've got 10 passes and everything is super noise. Once you get to a cleaner result I think you'll find that the noise is a lot more subtle. Unless something went wrong, heh :)Hey