There is only one person who can judge which codec is the best. First upgrade to the latest build and render small samples with the different codecs and options you see on your hardware to match the demanded filespecifications of both sites and compare it yourself with your source footage and the uploaded small example files.
You'll need to be connected to an HDR display in order to actually benefit from it, otherwise YouTube will automatically downsample it to your display chain's capabilities.
Now, just try delivering it with anything resembling original quality. That's the unfortunate part.