This may vary from project to project but my suggestion would be to follow this setup for humans:

Use UE5_ skeleton as your main skeleton where you place all animations, for humanoid characters.

Take all animations of the ue4 skeleton or your custom skeleton and retarget them to the ue5 skeleton.

in 5.4 you can automatically generate IK rigs with a single click, or retarget animations.

These rigs can be used in animb bp with:

retarget copy Pose from mesh

this setup can be used for all humanoid characters that are not rigged to UE5 mannequin skeletons.

this way you won’t need to retarget assets for all human skeletons, you retarget animations only to the ue5 skeleton. this will make your project less heavy since you won’t need to create all animation files per mesh. (this is really good while developing, cause you won’t need to retarget anim each time you make changes during development, you can retarget animations once you are sure that the setup is ready for publishing to all other meshes)

with this setup you can use all meshes with a different skeleton from ue4_skeletal to metahuman to any human skeleton that is different from ue5 sk just create ik rigs. in 5.4 you can do that automatically and eventually fix some settings.

see an example of this kind of setup in the public folder:

If you won’t use this setup you’ll need to configure by yourself your human animbp, you can take as reference animation blueprint samples: ABP_UE5_MM and ABP_UE4_MM