Cannot confirm any of these points (Win 10 pro, Thinkpad T490p). Everything is buttery smooth, and does exactly what I would expect it to do, both zooming and scrolling. (I only tied the touch screen, though.)
Maybe check your touchpad and touchscreen drivers.
It will be tough to keep up with Edge/Safari on their respective home platforms going forward. I've been trying to move over to Edge from Firefox on my Windows desktop just because it's clearly the future. Safari works best on my iPhone12 mini. When I get an M1 MBA, I intend to just use Safari.
I haven't been using Firefox for nearly 20 years because of a rendering engine, I've used it because of its features. In the last 20 years, most people have moved from desktops to laptops and phones, native app battery use and performance means a lot more than features.
Bugs from a quick play-around (comparing with Microsoft Edge):
* The zoom with touch pad has a weird latency not present in Edge.
* Zoom on touchscreen is janky and jumps around.
* Zooming in and then out often (but not consistently) stops working half way through the gesture.
* Scrolling behaviour while zoomed is wildly different to native apps like Edge. Scrolling is extremely fast and has some kind of acceleration.
* Pinching while scrolling on the touchscreen lags badly.
It just feels shitty. Firefox devs don't care about a polished experience on Windows touchscreen laptops and it's a dealbreaker for me.