Firefox Preview is built on the GeckoView engine, and loads pages much faster than the “Fennec” version of Firefox.
Mozilla has moved the address bar to the bottom of the screen, where it is much more accessible.
Instead of a tab view which lists all the tabs that are open, there is a dedicated tab window, and this is the homepage of the browser. You can access it from the Tab Switcher button next to the address bar.
The settings are pretty bare-bones, but you will find an option to enable a Dark Theme there. You can also change the default search engine, login to Firefox Sync to synchronize your bookmarks, history, etc.
Firefox Preview Web Extensions support?
Firefox Preview does not support add-ons for now. But a GitHub page reveals that the organization plans to add support for Web Extensions.
If you are wondering about ad-blockers though, don’t worry the browser has one built-in and it works great.