Modifier keys on Mac. Command (⌘) handles most actions: new tab, new window, find, print, save, zoom. Option and Ctrl each cover a smaller set, Option appears in full-screen mode (Ctrl+Cmd+F), and Ctrl handles tab cycling and the tab menu.
Preferences and Quit differ from Windows. Preferences opens with Command+Comma, the standard macOS app-preferences shortcut, rather than the Alt+P used on Windows and Linux. Quit is Command+Q, not the Ctrl+Shift+X combination Opera uses elsewhere.
Advanced keyboard shortcuts. Once enabled in Settings, the single-key zoom shortcuts on Mac use the bare + and - keys (matching the standard zoom row), while Windows and Linux use the 0 and 9 digit keys instead.