Florida stacks UM coverage unless you chose not to
Florida's rule is in Fla. Stat. 627.727. Subsection (8) lets an insurer offer a non-stacking UM policy at a reduced premium, subsection (3)(b) treats an underinsured vehicle as uninsured, and subsection (1) says UM is not reduced by a setoff against any coverage. The injury threshold for pain and suffering is in 627.737.
Read how stacked and non-stacked coverage differ in Florida, check what subsection (8) requires, or see how UM and underinsured claims are paid.