These are all unique and different projects with their own codebases, devs and issues. If you want to learn more, try searching for their official git repos. If you want to see a quick list of YouTube related apps, with screenshots, feature lists, and links to the project pages then I suggest using F-Droid with the IzzyOnDroid F-Droid Repo enabled, and just searching youtube.

For a bit more details on how yo do that check out my other comment lemmy.world/comment/15622037.