That's an interesting question. The biggest planters, Whigs in the Delta, weren't enthusiastic for secession. Smaller planters and those wanting to become slaveowners were more passionate. Davis was definitely a planter, but definitely for secession.
x: "...The biggest planters, Whigs in the Delta, weren't enthusiastic for secession.
Smaller planters and those wanting to become slaveowners were more passionate."
Obviously depends somewhat on your definitions of "Planters" and "middle class".
But South Carolina lead the secession movement and South Carolina was ruled by its wealthiest Planter class.
More important, dividing lines between Southern secessionist majority and Unionist majority regions were not a matter of the number of "middle class" versus "Planters", but rather, simply the % number of slaves.
The higher percent of slaves, the more secessionists and visa versa, the lower percent of slaves (i.e., Western Virginia), the greater percent of Southern Unionists.