You may simply install many browsers and then experiment, to find out which one works best with YouTube videos, for your hardware / drivers, all depending on your needs.
You may wish to switch between html5 and Flash, for YouTube video playback,
by clicking here (choice may not be available for all browsers).
This page will also allow you to know what your browser supports.
The Flash Plugin comes in different flavors, depending on your browser:
Adobe Flash Player Install for all versions
On my XP32 laptop, they all have the same performance.
Now for browsing, I personally use
Pale Moon. But I keep
Opera 12.18 at hand, because it uses very little memory. Therefore I can (barely) load 2 browsers at the same time, in 1 Go ram. I point out Opera 12.xx is outdated.
On my browser / hardware, Flash works better overall for YouTube video playback.
On Firefox-based browsers, these extensions can be useful:
YouTube Flash Video Player
YouTube High Definition
Download YouTube Videos as MP4
Lastly, I point out most browsers can not render
360-degree videos properly. I know Chrome can. Maybe other browsers can too?