There's been a few comments on here talking about Firefox on Android being laggy compared to Chrome on Android.
Nobody seems to have mentioned this, but the main reason this is and/or appears to be the case is because Firefox is capped at 60Hz, whereas Chrome will display at 90Hz, making it feel much smoother.
No, I have no idea why.
Edit: The above is misinformation after I did some research - it appears that resisting fingerprinting causes the browser to set itself to 60Hz, but this can be disabled to get your screen's refresh rate, but of course this means throwing away a privacy protection...
Could be one of those "optimisations" some brands make. I wasn't getting 120Hz on all apps on my OnePlus device. I had to force it with developer options or some 3rd party app. Gave up, installed a custom ROM (LineageOS), and it's 120Hz all the time without any issues 😎