Firefox Beta and Firefox Preview are a bit different. Preview and Focus are both currently a bit more experimental, they're stable but they're not guaranteed to be kept alive. Firefox Beta and Nightly are both the current latest versions of what will be merged into the stable.

There's a big rewrite being done and the current stable Firefox for Android which supports basically all addons that the desktop version does, will be deprecated soon-ish. Preview has a broader support.

Beta and Nightly only support uBlock Origin, literally.

Preview supports six addons in all, but Preview isn't a promise of whats to come as they consider it a pilot.