Firefox is alright, it served me adequately after Opera got sold off, but Vivaldi is so much better.
Even though it's based on a fork of chromium Vivaldi has an extremely strong focus on innovation as well as privacy, they've commited themselves to working around Mv3 for instance and their in-built ad-blocker is absolutely top notch but you can also install uBlock Origin to work with it in tandem on their desktop browser if you want.
And even though it's extremely feature rich, with speed dial, ad-blocker, password vault and side bar being some of their out of the box features all their power user functions are opt in through the settings where you can choose to stack your tabs vertically or enable mouse gestures (couldn't live without these) and a whole bunch more, it really offers everything you could think of and probably a whole bunch more.