I can add a bit to what you have on James Tucker, but nothing on your James L. Turner.
Rose Mary Lankford's "Encyclopedia of Quantrill's Guerrillas" on page 264 asserts from several sources that this James Tucker was in Quantrill's band during 1862 and even made 3rd Sergeant in the group that summer.
In Eakin and Hale's "Branded As Rebels" on page 437, they repeat this information and add that sometime after August 1862 James Tucker joined "the 12th Missouri, Shanks Regiment, Shelby's Brigade, CSA."
In this same work on page 121 we read that Captain James Tucker brought a recruiting command up through SW MO from Arkansas back to west-central Missoui in about July 1863. ("Branded As Rebels" mistakenly wrote that as "July 1862," but that was improbable since Tucker was named 3rd Sergeant in Quantrill's band in August 1862.)
In Captain Quantrill's own report he filed on his way to Texas on 13 October 1863 in his postscript ("O.R." series 1, vol. 22, part 1, p. 701) Tucker's former commander wrote: "In this report I neglected to say that Colonels [John D.] Holt and Roberson and Captain Tucker, who have been in Missouri on business for the army, were with me, and took an active part in leading the men on the enemy."
From these sources we can assert that:
1) James Tucker was during 1862 a guerrilla under Quantrill;
2) some time after summer 1862 James Tucker joined the 12th Missouri Cavalry or Shanks' Regiment of Shelby's Brigade;
3) that during about July 1863 Captain James Tucker led his own recruiting command north through SW MO back to west-central MO to recruit for the Confederate army; and
4) Captain Tucker brought his recruiting command successfully out of Missouri in early October 1863 by riding along with Quantrill's large band on their way south.
This adds credibility to the information on James Turner's card that he enlisted 1 August 1863 in Jackson County under Captain Tucker.