They are all destructive: trim, cut, normalize, silence, fade in, fade out, and remove DC. They’re destructive in the sense that they actually modify the waveform. There’s no single undo. There is a revert option that undoes everything you’ve done at once and restores it back to the original buffer state.
These operations are just affecting the buffer in RAM, and not being auto-committed to disk. So when you’re finished you can just do a save as from the file operations further down in the menu if you want to make a new file with your changes, while preserving the original. Possibly you can do a save as before you start editing if you want to make an identical copy of the original.
I’d recommend experimenting on some throw-away wave file, just to get comfortable with the workflow.