Control Rig in unreal engine does NOT mean your armature or rig in the same sense as Blender users use the word rig. Instead Control Rig is Unreal Engine’s way of defining Blender’s Custom bone shapes, bone constraints, bone drivers and custom properties all into one system.
Blender's Custom Bone Shapes In UE5 Control Rig
What’s known as “custom bone shapes” in Blender is called controls within unreal engine’s Control Rig. These are the yellow,green,red… shapes you see around a character when they demo UE5’s control rig. So Custom Bone Shapes are a system within Control Rig.
Blender's Bone Constraints In UE5 Control Rig.
To Create Inverse Kinematics or IK in blender, you use bone constraints.
Well, Constraints in unreal engine are created using Control Rig’s Nodes.
For example the constraint needed to do IK would be called IKTwoBone in the control rig node graph whereas in blender you would use the bone constraints tab.
Other types of blender constraints that establish child-parent relationships, location, scale and rotation constraints can also be defined in the Control Rig node graph.
Blender's Bone Drivers In UE5 Control Rig.
Bone Drivers from blender can be implemented in Control Rig. Compared to Control Rig, Bone Drivers in blender are limited and tend to be slow. Control rig has nodes for bone driving and can do the same as blender’s bone drivers but can do even way more. Fully unlimited bone driving using nodes for scripting.
Blender's Custom Properties In UE5 Control Rig.
Custom properties In Blender are usually used with bone drivers to drive poses and more. You can implement custom properties in UE5 Control Rig by using variables and wiring them up using the Control Rig graph nodes. Your custom properties/variables will drive your bones just like in blender.