I donate to the Mozilla foundation, and I love Firefox a ton. But I can't seem to like the UI by installing a theme, and when I change it to look better the browser slows to a crawl. Does it really matter all that much if I use Chromium?

P.S. To the people from my last post regarding something similar, Firefox was too slow, I'm sorry, but I use Vivaldi instead of Brave because Brendon Eich can suck my dick.