Missouri was. A rump faction of the Missouri legislature, on the run from Union troops, voted MO out of the Union. While the CSA considered MO a Confederate state, most Missourians did not. Probably more than twice as many fought for the Union than for the CSA. A similar scenario played out in Kentucky.
North Carolina was. Nope. "We, the people of the State of North Carolina in convention assembled..."
Virgninia was, too. Nope, again. I happen to be fairly familiar with the Virginia Convention, as it voted secession down by over 2:1 before Sumter, then reversed itself by the same proportion after Sumter.
The political theory of the time was that a Convention spoke directly with the voice of the People, whereas legislatures were composed of politicians. This theory appears to have largely disappeared without a trace. Also I believe Conventions were held to ratify the USA Constitution, so the theory was that a Convention was needed to secede from the USA.
Read some history instead of the preambles of the documents. South Carolina’s convention was selected by their legislature, not the people. North Carolina’s population voted against secession, the legislature took them out anyway. Missouri’s secession convention also voted against leaving the Union, which the governor tried to do anyway. Virginia’s legislature voted secession and the state was admitted into the confederacy before the popular referendum was held. In most cases ‘the people’ had little or no say in staying or leaving.