Here is a brief summary of his NARA records.
NARA Records Samuel K. Reed
Private Co. F, 1st Regt Arkansas Cavalry (USA)
Age 24
Enlisted Nov 17, 1862 at Fayetteville, ARK
Roll dtd Jan-Feb 1863
Absent - Detached duty Assistant Wagon Master
Roll dtd Mar-Apl 1863 --same
Roll dtd May -Jne 1863 --same
Same for every roll, but some were marked Present
Mustered out Aug 31, 1865
I have a "relative" in my family who was detailed as a Wagon Master and one comment indicated he carried wounded men to the hospital. I wonder why he was absent so many times. I guess he could not keep up with the regiment.
So, I would say he may not have been heavily armed. He could have had a pistol but may have carried a big gun in his wagon much like the guards on ole West stage coaches. So the answer is probably Yes for both; the studio photo probably used props and he was armed on duty.