Of course, the biggest change with the characters is the gender-flip of Jonathan Higgins to Juliet Higgins (Perdita Weeks).
In terms of the plot, the faces are in their respective roles helping their fellow war buddy.
As opposed to Vietnam, the men served together in Afghanistan before falling into their respective positions in Hawaii.
The character doesn’t see a massive change beyond that in the pilot episode, although one would suspect Thomas and Juliet may have a different relationship than Thomas and Jonathan had in the original.