I think vivaldi is respectful of the users privacy, and they are very transparent. If privacy is important to you, they have a number of settings which can be toggled to make it more private and secure: https://help.vivaldi.com/desktop/privacy/privacy-settings/

The rendering engine is chromium, and that’s a deal breaker for some people. If you don’t care about that, then I think it probably ranks right up there with Firefox.