Changing Emoji Shortcut
This will work everywhere that Emoji &amp; Symbols has a menu item...

System Prefs &gt; Keyboard &gt; Shortcuts &gt; App Shortcuts
Click 'All Applications'
(hidden in the picture)
Click +
Type Emoji &amp; Symbols in the first box
Type your replacement trigger in the second
Click Add

 As noted in comments, Cmd/Space is usually used for Spotlight. I chose this almost at random &amp; discarded after the picture was taken.