The Snap is by Ubuntu (and presumably will still be the way Firefox is installed by default on Ubuntu). I think that this is for people who'd prefer not to use the Snap, allowing them to install the .deb directly from the source.
Firefox for Android can now be set as the default PDF reader.
Firefox for Android now supports enabling Global Privacy Control. With this feature, Firefox informs websites that the user doesn’t want their data to be shared or sold. This feature is enabled by default in private browsing mode and can be enabled in normal browsing in Settings → Enhanced Tracking Protection -> Tell websites not to share & sell data toggle.
To reduce user fingerprinting information and the risk of some website compatibility issues, the OS version is now always reported as "Android 10" in Firefox for Android's User-Agent string.