When rendering a 4:4:4 video, does the source have to be TIFF? Or can you create a 4:4:4 chroma video out of JPEGs?
Jpg is 8 bit only. So it would be better to use tiff to have any advantage when rendering in 444.
When exporting as JPEG (LRT JPG, ORI), what are the specifications of the JPEG file? Is the quality set to 70 or something?
Also, would JPEG be sufficient for 4:2:0 rendering?
Normally yes, since you do all the color and contrast editing in Lightroom before you export...