When I moved to Hugo with my website, I looked to optimise everything and implement new techniques. Once Safari gain native WebP support back in 2020, I implement WebP following PawelGrzybek.com - WebP and AVIF images on a Hugo website. The post introduced not only how to implement WebP (at the time when Hugo <0.83 haven’t support it), but also shown how to go step further by implementing AVIF.
This method require you to have WebP/AVIF files stored along with PNG/JPG and not relay on rendering them when the site is build.
I was interested in implementing this as well, but after some tests in my environment I decided not to, and here I will explain why (and it is not about browser compatibility — Safari incompatibility).