Installing sliding door into a larger rough opening
Yes you can put a smaller door in, going smaller is easier because the header is already there, make sure when you frame your smaller door to leave a little room and make sure it is square x measure from corner to corner. I have helped a bunch of friends that made their opening exact and could not get the new window / door in because it was not exact or there opening was not square. 
Extra wide trim on the outside can look like an expensive upgrade some don’t have a clue why we would do that.