The betterfox guide available in GitHub provides many tweaks for faster and smoother browsing experience, even there are preferences for 120hz display, 90hz display..so why can't firefox natively take advantage/enable a set of preference after determining device capability? For example if someone is using 120hz refresh rate display, firefox should tweaks those preferences which will give a smoother experience... similarly if the device has larger RAM which is pretty common these device, firefox should tweak the settings to maximize the speed and experience.
Personally I am using a 12GB RAM phone with 120hz display and tweaked some preferences as per betterfox, now it is faster and smoother than any other chromium browsers..even chrome will shy away.
Unlike desktop it is painful to edit settings one by one, please consider the same and enable some settings ,(automatically based on device capability or some end user settings so that user can enable manually, which will result in modification of bulk of preferences for that purpose)
Reference: https://github.com/yokoffing/Betterfox