4chan

No one has mentioned Vivaldi yet. I haven't found it slow in the years I've used it. It does hog memory with the amount of tabs I open, but no more than any other browser I've used. Fortunately it has inactive tab suspenders as an option to help with my bad habits (natively now, and through chrome extensions before that). Also, it is undoubtedly the most visually customizable browser I know, so it being ugly is really you making the sandwich.

If this was just bait, I guess it got me. If not, anon could try Tor if they value privacy, or maybe something minimalist if they really care about performance.