After the 54 release, it is the better browser frankly, low latency, and not a resource hog. Plugins, extensions, privacy and security defaults all seem to be better as well.
Using firefox focus on android is pretty great too. The normal firefox on android is just slow, not sure why.
I believe Firefox Focus (on Android and iOS) uses the OS native web view (effectively, Chrome or Safari), but the actual Firefox for Android uses Gecko.
^ This seems right from my quick googling, there is this project for a gecko webview, which needs work: https://wiki.mozilla.org/Mobile/GeckoView and mentions firefox focus' gecko build option.
Firefox on android is too slow to use a lot of times. Something mozilla should be able to do better.
Using firefox focus on android is pretty great too. The normal firefox on android is just slow, not sure why.