A recently published support document highlights Mozilla’s plans for the current Firefox for Android and also Fenix.
Mozilla’s main idea is to maintain the legacy version of Firefox for Android until Fenix reaches migration readiness status. Firefox users on Android should be able to use the legacy version until Fenix is ready while Mozilla wants to minimize support costs.
Fenix currently does not support extensions just yet, so I’ll be staying on the regular Firefox for Android until that has been addressed.
Actually it already seems to block ads and that is the only extension I used on FireFox for android before… I’m going to give it a try for a few days and see if it stays as fast as it is now or if it ends up bogging down after use.