Regarding that controversy it is clear only Davis as commander in chief and president has the authority to surrender all forces and to negotiate peace.
He was not the president of the CSA, he had not to my knowledge communicated with Davis his plans to surrender the AoNV.
His authority was limited to military issues.
Ultimately.
Davis gave Lee, the General-in-chief of the Confederate armies, an authority negotiate a conclusion of military operations in January, 1865. Davis:
Nothing came of that. However, within a few weeks, the armies were discussing prisoner exchange issues about Petersburg, and Gen. Longstreet suggested it was a chance for Gen. Lee to initiate a peace nation-wide by meeting with General Grant under some other ostensible object. Longstreet later said Lee would have done well to have acted instantly and of his own authority, but Lee insisted on discussing with Davis.
Davis gave Lee authority to conclude hostilities, or the war, if possible, by a military convention with the US forces, on February 28, 1865:
It appears Davis preferred some sort of possible concessions from the USA from such a convention. In any case Lee noted to Grant he was authorized to "do whatever the result of the proposed interview" might render "necessary or advisable"...
General Grant sent notice to Washington of the apparent fact of a possibility of negotiating a general disbandment of CSA forces, or giving Gen. Lee an opportunity to surrender the same. President Lincoln, preparing for his second inaugural on March 3, informed Grant to not concern himself about other than a military victory against Lee's Army of Northern Virginia... and this was communicated to Gen. Grant, with War Secretary Stanton's signature:
Grant replied to Lee on March 4:
On the 13th Davis declared that the USA would accept no terms of any kind, from
any Confederate authority. From this date, then, apparently, Gen. Lee was constrained not to discuss any but purely military issues with the US forces, by both the US forces, and his own commander-in-chief:
After the "final issue" Lee surrendered himself and the Army of Northern Virginia to Grant at Appomattox, Grant apparently informed Assistant Secretary of War C.A. Dana that Lee informed him he had been prepared to surrender the entirety of the Confederate armies by the lately proposed military convention...
Once Lee was defeated, and surrendered in the field, it was evident the Confederacy was over.
The balance of the Confederate armies were surrendered by
Military Conventions with the US Army, etc. Davis was present in North Carolina when Johnston began discussions with Sherman. He wanted some terms, if possible, but ultimately, the surrender was
unconditional.
Where it gets cloudy is in the mechanics of a confederation founded on limited central powers where theoretically the states held equal power to the central government. Would each state have to approve any surrender?
Yes, murky.
The Southern Confederacy had a rather
unlimited, limited central government in some respects. The Confederate system did not see any distinction between the States and
their Confederacy. Take the "State Sovereignty" theory, and combine that overwhelming idea of sovereignty, (more powerful to its enthusiasts than the Constitution or the Union of the United States) into the Confederate Government. A sort of attempted manifestation of Calhoun's 1851 theory of "a confederacy of sovereign states." Davis at the head.
General Beauregard later commented from an interview at New Orleans...