I haven't upgraded from Mojave but I've also been daily driving Safari for the last few years. I gotta admit that in the butt dyno department everything feels significantly faster than any other browser. I made the switch when I realized how much more power efficient it is and haven't looked back.

I only use FFX and Chrome for testing, although I tend to use FFX a lot for the developer tools and Vue integration. That being said, Safari has extremely polished dev tools that are highly capable.