Strut suspensions do not have an upper ball joint or control arm. The upper strut mount turns as does the entire strut assembly, replacing the need for the upper control arm and upper ball joint, so strut suspensions are cheaper to manufacture and work great on cars and vehicles that do not need as much suspension travel as 4x4 off road vehicles do.
The FJ has a coil-over shock setup stock, it is non adjustable and spring rates of non adjustable coil-overs cannot be compared to spring rates of adjustable coilover's because the spring rate of any adjustable coilover will be different depending on the preload of the coil.
Aftermarket coilovers are adjustable, normally add some travel, shock dampening, spring rates, flex, ride, front weight capacity and desired lift. They are different but look similar in design.
The FJ does not have a strut suspension. :clap: