It's an interesting question. The transports were unarmed, and hired less than six weeks before the movement.
The ships used were hired by John Tucker, and
he supplied a list when a scandal broke regarding misappropriation of funds. The list does not include ships hired by anyone else (the minority used). For example, I know which ships 6 regiments of Richardson's Division went on, and two went on the large mail steamer
Ocean Queen, which is not on the list. This is because the
Ocean Queen was hired by the Sanitary Commission as a hospital ship, and pressed into one run as a trooper.
Irish Brigade - 2 regiments (69th NY and another) were transported in the large
Ocean Queen, and the remaining one in the
Columbia.
Howard's Brigade - The large
Spaulding carried the 81st Pa and 61st NY. The 5th NH was split across two ships; the
Donaldson (6 coys) and
Croton (4 coys and the brigade baggage). The 64th NY did not go in the same convoy.
At least one large steamer on the list was not used as a transport, but transferred to the USN on 24th March to become a
warship.
The steamers used to carry men ranged from some really large mail steamers, which could carry two regiments, down to small steamers which could carry half a regiment.
The real problem was horses. Schooners were used to transport horses, and a typical one carried ca. 40 horses or other animals. Consider a battery of artillery alone needs 3 schooners for her horses (and another few for her vehicles), or a cavalry regiment needs ca. 20 just for the horses.
As a note, only the first six divisions landed near Ft Monroe. Richardson's and Hooker's divisions landed at Ship Point after the army had reached the Warwick Line. The engineers built a new facility at Wormley's Creek during operations much closer to Yorktown which allowed easy supply of the army (even Ship Point was far enough away that supply was difficult), and that was where Franklin's division disembarked.