No. ShapeKeyFX writes ordinary shape key keyframes. The result plays, renders and exports on any machine or render farm, even without the add-on installed, and the built-in Alembic and OBJ export takes it to other applications.

No. It only writes curves for the shape keys you assign to tracks. A key that is already animated by another track is refused, and if a key has a driver ShapeKeyFX warns you, because drivers override keyframes.

Yes, that is what it is built for. Sculpt the dent on a shape key of the body mesh (belly, glutes, chest, thighs, face) and animate the contact with hands, props or other characters. Shape keys deform before the Armature modifier, so the dent follows the rig.

Yes. The Export section writes an Alembic cache (Unreal Engine imports it as a Geometry Cache) or an OBJ sequence (one file per frame, with a JSON info file for loaders in Godot, Unity and others), with one-click unit presets for Unreal, Godot, Unity and DAZ Studio.

No. There are no handlers, drivers or simulations running during playback, so scrubbing, looping and rendering run at full speed. The keyframes are only rewritten when you change a setting.

No. ShapeKeyFX works fully on its own. The optional SpringFX Kick section only becomes active when SpringFX 8.5 or newer is installed, and lets every hit push your bone physics as well.