In the current version of Word, the window bottom still has buttons for switching views (Print, Outline, Draft, etc.), shows Page X of Y, the number of words, an icon for the spelling and grammar checker, and a slider for zooming in or out. If you right-click a blank spot in the bottom window “chrome,” you can turn on and off a number of tools. For example, it doesn’t show the section number by default but it can, another is a button to toggle whether Track Changes is on or not.
(I made the window very narrow just to make this screenshot smaller)
There’s a Styles button to show a dropdown of styles (with previews of the styles) which expands to a horizontally scrolling list (that can also be a dropdown) when the window is wide enough. If the window is wide enough to show the styles, the style where the cursor currently is will be highlighted (but it won’t automatically scroll to make that style be within its viewport). I think this is called the Quick Styles list and you can edit which styles are included in it.
The Styles Pane button is different, clicking that displays a sidebar which shows the current style (where the cursor is) and a list of styles that can be applied (there a choices for which styles are displayed in the list). I don’t know to what degree styles can be navigated and applied using only the keyboard. Microsoft’s Keyboard shortcuts in Word for Mac only lists ones to copy and paste styles plus a few for applying common styles like Normal, Heading 1, etc. It also mentions changing macOS’s Full Keyboard Access setting to All Controls to use the ribbon by keyboard alone; I can use Tab, Shift-Tab, arrow keys, and space bar to navigate the ribbon, go through the quick list of styles and select one; I couldn’t do something like type the first letter of a style to jump to it. I didn’t see an option to create keystrokes but you can edit the ribbons, changing their contents and order.