Are you sure? IIRC :x only writes the file again if there's a change where :w(q) always writes again (which takes longer when editing a remote file via scp://). For a non-exiting version of :x there is :up. I bound :up to <leader>fs after I learned about it. I used to have :w on the same keybind so it was a straight upgrade. Now I can just quick hit it at any time and there's no waiting around if the file hadn't changed. Saves some time and annoyances.

Yes, through ":help wqa" which lists it as such and double checking with a quick test. It doesn't write unchanged files, same as :xa instead of being an exact "all" version of :wq