I am a little familiar with the 4th Cavalry Regiment, Powers', although Co. G, and not E.
My gr-gr-grandfather, Thaddeus Samuel Stampley, enlisted in 1862 in this unit, a few months shy of his 15th birthday. This company spent 99% of its time in southwest MS (Adams, Wilkinson, Amite, etc. counties) and around the Port Hudson area in Louisiana. They were not part of the ANV. The Adams Troop was the only MS cavalry unit to serve in the ANV.
Hope this helps.