A perfect browser don't exist, it can only be at an individual level, depending on the needs and activities of each user.
Although Vivaldi, due to its great possibilities of adapting it, comes pretty close, it can be unusable for some users, either because it is overcapacitated, because they only use it to check email and little else, or because they have very basic and old equipment, which gets red-hot with Vivaldi's minimum specifications or its not longer compatible, among other reasons.
Since Yngve's article, I've been testing Vivaldi running without sending any Client Hints, and not noticed any site issues - at least on the sites I use daily.
I believe Client Hints is just Google once again forcing their own invented "standards" on the web, by reducing the UA in Chrome and forcing sites to adapt to Client HInts - which of course give much more information about the user's system than the UA string, hence improving fingerprinting and tracking.
Web developers (the stupid kind, of which there are many) will be able to fine-tune their responses to specific browsers and OS, effectively locking out anyone using minor-league browsers like Vivaldi: "We only support the most recent Chrome and Edge browsers".