I've drafted up the following re this subject for my regimental history of the 43rd Tennessee, CSA.
It should be noted that Union companies had 8 Corporals, Confederate, only 4.
Other than their placement on parade, I have not been able to discern the differences between the Second through Fifth Sergeants, and likewise the corresponding First through Fourth Corporals.
An excellent description of the duties of the Orderly (First) Sergeant is found in William Watson's "Life in the Confederate Army, Being the Observations and Experiences of an Alien in the South During the American Civil War," Louisiana State University Press Edition, Baton Rough, 1995, pp. 140/141
Each infantry company contained about 100 men. A Captain and three subalterns, First, Second and Third Lieutenants, the latter at times called a Brevet Second Lieutenant. The senior non-commissioned officer was the First, or Orderly Sergeant followed by four Sergeants noted as Second, Third, Fourth and Fifth Duty Sergeants. Then came the four Corporals entitled, First, Second, Third and Fourth Corporals. In addition, each company had, for the purpose of sounding the different calls to order, a Drummer and a Fifer.
The company was further subdivided into two equal parts designated the first and second platoons. Each platoon in like manner was divided into two sections. [Hardee’s Rifle and Light Infantry Tactics, for the Instruction, Exercises and Maneuvers f Rifleman and Light Infantry, Brevet Lieut. W. J. Hardee, J. O. Kane Publishers, New York, 1862, p. 5]
To guide the regiment in its duties were the regimental Field and Staff, abbreviated F & S. A staff of three officers commanded the regiment, a full Colonel, seconded by a Lieutenant Colonel and a Major. Additionally, the staff consisted of an Adjutant with the rank of Captain, an Assistant Quartermaster (A. Q. M.) and an Assistant Commissary Subsistence (A. C. S.), both Captains. Rounding out the F & S were a Chaplain, a Surgeon and Assistant Surgeon. The enlisted staff was led by a Sergeant Major, the senior regimental Non-Commissioned Officer (NCO) and consisted of a QuarterMaster Sergeant, a Commissary Sergeant, an Ordnance Sergeant and a Hospital Steward. Additionally, the regimental staff consisted of Forage and Wagon Masters; Fife and Drum Majors; a Sutler; Blacksmiths; Teamsters; Wagoners; Ambulance Drivers, Nurses and Clerks. Each of the latter retained the rank of Private. Also, each company was authorized two Laundresses/servants. [Note, Regulations for the Army of the Confederate States, 1863, Article XIII, Section 121, notes: "Four women will be allowed to each company as washer-women, and will receive one ration per day each."