WebP files are typically 25–35% smaller than JPG at the same quality, which makes pages load faster and helps SEO.
Yes, every modern browser (Chrome, Safari, Firefox, Edge) displays WebP images.
For websites, 2048 px on the longest side is plenty. Choose it under 'Max dimensions'.
No. Everything happens inside your browser, on your own device. Your photos are never uploaded, stored or seen by anyone.