Are IntelliJ IDEA's keyboard shortcuts the same on Windows and Mac?
No, not directly. IntelliJ IDEA ships two separate default keymaps that each follow their own OS's conventions. Some shortcuts are a simple Cmd-for-Ctrl swap, but many others use entirely different keys, tool windows are Cmd+1-9 on Mac versus Alt+1-9 on Windows, for example.
What's the fastest way to find a file or action in IntelliJ IDEA?
Double-tap Shift to open Search Everywhere, which searches files, actions, symbols, settings, and recent locations in one box. Ctrl+Shift+A (Cmd+Shift+A on Mac) opens Find Action specifically, for running a command or opening a setting by name.
How do I see every refactoring available for the code under my cursor?
Press Ctrl+Alt+Shift+T on Windows or Ctrl+T on Mac to open Refactor This, a menu listing every applicable refactoring, rename, extract method, move, safe delete, and more, for whatever's at the caret.