Why does Ctrl+N open a browser window instead of a document?

Because the browser claims it before the page sees it, and a web page cannot override that. Ctrl+Alt+N makes a new document here instead. Installing the editor as an app gives it a window without the browser's own shortcuts competing.

Do the Mac equivalents work?

Yes. Every binding is expressed against a modifier that resolves to Command on macOS and Control elsewhere, and the few that differ for real — redo is Command+Shift+Z rather than Control+Y — are listed that way in the sheet on a Mac.

Is there a shortcut for track changes?

Ctrl+Shift+E, the same as Word, and Ctrl+Alt+M inserts a comment on the selection. Both are in the Review group of the sheet, along with the accept, reject and next-change commands.

Can I see every command without memorising anything?

Press Ctrl+/ for the command palette and type. It searches all the commands the ribbon holds, shows the keyboard shortcut next to any that has one, and runs the one you pick — which is also how most people end up learning the shortcuts.

Word Keyboard Shortcuts That Work in the Browser

The Word shortcuts that do the same thing in a browser tab — formatting, navigation, review and references — and the handful the browser keeps for itself.