This sounds good as the bottom makes more sense as if you are reading a longer comment you want to upvote at the end, not have to scroll back to the top to upvote

I agree, this would be great

I think that it would be great to have an option to expand all images by default, possibly at 50% size for easier scrolling, the UI does look great rn

would recommend https://addons.mozilla.org/en-US/firefox/addon/youtube-addon/, idk if 100% of the features you mentioned are on there but worth a try

I have a bit too much louie zong on my playlist

Yes, that would be great

Firefox, but if you do need a chromium based browser try ungoogled chromium