USA Captain
Yes, your rank will be displayed on your uniform.
If you are a First Sergeant, you will have a First Serg. badge on your frock coat, while a Sergeant Major will have his own unique badge and outfit.
There is a single NCO class, but the visible uniform/rank depends on your ingame rank/ later your company rank.
USA General of the Army
Rest in Peace to Hinkel, the unofficial/official first casualty of War of Rights.
So what did happen to the Major rank and up in the companies?