There is no way to achieve that through youtube plugin which us using only iframe.
It’s not that we didnt create a solution, actually its not possible to hide all the branding.
There might be a possible solution if you use youtube API, but I’ve never used that, so I dont know.
Only solution if you dont want to see branding is to upload videos directly on DH, not going through youtube or vimeo, or any other 3rd party service.
I am not sure, but there might be a possibility that youtube and vimeo have some video optimizations that regular video doesn’t have, including loading times, etc. But I can’t confirm that without any research.