There are two in total: the 3×3 ‘Quick Actions’, which has a search bar and Home, Shorts, Subscriptions, and Library buttons. If you have a 5×5 or 3×3 grid, at 3×3 size it can only display 3 buttons, like in the preview.
The second widget, Quick Search, basically looks like the first widget without the bottom row of buttons and just serves as quick access to text and voice search.
These widgets are available by default in the app version 17.43.35. Earlier similar widgets appeared on iOS, only the search widget was a 2×2 square.