Firefox for iOS alternatives

Actually I'd like to review browser more than calendar, because calendar is more simple by design, but the browser is more important for me as Internet user. I have used both Vivaldi and Opera. My experience with both has been positive. I like how much personalization you can do with the two browsers. It is a little more difficult to find settings in Vivaldi than Opera, but once you find them its not that much more difficult to change. I would say that after using both browsers for a while I prefer Opera.