Your email helped me understand how it works (the big picture). I am sure I can find a good solution in one of these two formats.
Yes, it was the same thing. I am so so bad with mailinglists..I searched for my previous mail and I could not find any trace of it so I posted another one.
Sorry for that.
Thank you for the clarifications. I will take my time and read it again. I must say that I managed to get great results with jp2 and webp format. I decreased the size to ~50 from ~270 and the quality is very good.