Format idéal pour vidéo motion pour Youtube

I found that after much experimentation that beause YouTube also compresses footage, it was simpler to render out at Match Source, High Bitrate.  I used to use the presets, but YouTube is constantly evolving its processes so I make the video the highest quality I can and leave YouTube to it.  Adobe's preset makes for smaller videos but as you've found when it goes through YouTube's own routines the quality loss is noticeable.

Also worth remembering that YouTube is a streaming service and includes bandwidth detection - it might be that your YouTube playback settings have been set (or set for you) to a lower quality.  On your own website are you streaming or have you embedded the mp4 file?

Either way, my suggestion would be to render out at ProRes then take that video file and run it back through AME twice, once nicely compressed for your website and once at match source, high bitrate for youtube (you can always delete the files after).

You have to learn by just doing it. As @nishu_kush already said, the default presets work just fine, but of course there's always the potential for improving matters both by tweaking the encoding options as well as optimizing your artwork to produce less artifacts. This is nothing you can learn from tutorials, it's a matter of experience and developing a feeling for these things. The general point sticks, though: You have to accept some losses in quality on occasion simply because you have no control over the server-side encoding and streaming of the video service providers.

Mylenium

There is no solution. You have to accept that YT re-encodes your footage and produces multiple versions for its adaptive streaming. You can only control this minimally if you have a Pro account and play with the data rate allotment in the Studio editor where you also can enforce only publishing high-res versions, but otherwise this is a case where you really can't do much. If it's that critical, you may want to find alternate video/ upload services but even there you have to accept some of these  limitations.

Mylenium