> [JPEG XL can] display much larger images than AVIF can
Does it do tiles? What about pyramids (i.e. precomputed downscaled images, think mipmaps)? Right now the state of the art for truly large images (medical, geospatial, scanned artworks) seems to be JPEG (and I think also JPEG 2000?) tiles in TIFF containers, which would be fine except nobody seems to agree on how exactly to express the pyramids.
Level 10 spec is 2^40 pixels, which is a ~1 million x ~1 million pixel square.