My reading of history suggests the Deep South cotton states seceded mainly over slavery... they pretty much said so in their convention debate records.
Border states like Tennessee and Virginia seceded later, and probably had additional concerns, like being invaded, and not contributing 75,000 volunteers to Lincoln in order to be invaded.
My great grandfather was a farmer in West Tennessee, aged 21 when war started. I expect he fought not for slavery or constitutional principles as much as because his three brothers and most of his friends all signed up with the Yorkville Rifles (later the 13th Tennessee Infantry regiment). They had about 90% casualty rate. I bet he would later probably judge it all to have been not worth it, as a practical matter.
Pardon the hijacking from Nazis and statues.