It's a question of balancing comfort with how much you are willing to carry, and every soldier seems to have made that decision personally. In photographs one sees men with blanket rolls, knapsacks, neither, and both. A clean shirt and socks after a long, hot march (or one on which you get soaked) can really be worth the weight of packing them. It also depends on circumstances. It seems that many soldiers would leave their knapsacks with most of their less necessary gear in the baggage train for long marches and such, only carrying a blanket roll with the bare necessities.
For example: in November, 1863 Echols' (1st) brigade was camped near Lewisburg, (West) Virginia. They received orders to march north to the support "Mudwall" Jackson's cavalry brigade, which was facing Gen. Averell's 2nd raid. Tents and knapsacks were left in Lewisburg. Therefore:
1. The men had less to carry and could march faster before Averell crushed the vastly outnumbered cavalry
2. If the CS won, the baggage train could catch up after a couple days and the men would have their stuff
3. If the US won, they could retreat faster
(In the event he US won but the knapsacks were accidentally left in Lewisburg and destroyed by a Union flanking column)
Knapsacks would typically contain extra shirts and underwear, soap, a comb, a toothbrush, a shelter tent or oilcloth (or poncho), an overcoat (men often ditched these in summer, or left them in the wagons), socks, perhaps a deck of cards, reading materials (the most common of which was the Bible), pen and paper, personal items such as photographs of loved ones &c., perhaps string and other useful oddments. If a blanket roll wasn't worn there were various ways to attach it to the knapsack, depending on the type. What a person carried depended on the individual, and more experienced soldiers (as others have mentioned) tended to carry less. Some men were slobs who wore the same clothes until they rotted off their backs, while others were fastidious about keeping clean when practicable.
On their person they would carry what any man of the period typically did- knife, wallet, and sometimes a watch and handkerchief.
I believe that's what you were referring to by "everyday items" (viz.- personal items?). If I may be so bold, what is your intent? Are you writing a paper? A book? Do you plan to reenact?
If either of the latter, remember that WHO the man portrayed is will determine to a substantial extent what he has, how he wears it, and how he acts. A seedy loafer didn't have much in common with a foppish swell or a solid gentleman, and all three (and more) jined the army.
Did not intend to be so lengthy. This article (
http://acws.co.uk/archives-military-equipment) is a good source of more information.
Also (I promise this is the last thing)- you may wish to look at period photographs- Library of Congress has quite a few in very high definition online, though the Rebs are mostly gone beaver, often grotesquely so.
D.H.