Select a youtube resolution and resize the player.
Thanks for the suggestion. The reason I never implemented this was because different userscript extensions have different APIs for this. While I can write code that will work for all of them, at the time I didn't want to make the script twice as complex when the intention was to not have to update the script frequently if at all. Although in the end I did have to update the script more than I expected to due to browser changes and youtube overhauling their website.
If this is something people really want, I can add it. Currently I still would prefer to not make the script more complicated though, because if user script extensions change (like they have before) then the script breaks for everyone, and the current way is less prone to breaking from ecosystem changes. For anyone else who want this feature added, please let me know here.
Is it possible for you to add a "setting" for targetRes to the script, so we could set it once instead of having to change it each update? Maybe for the other features as well.
To clarify, if you don't know what i mean is sometimes scripts have settings you could tweak like shown in the annexed image.