This video goes over the process of how to setup a Full Body IK solver for bipedal characters for IK Retargeting. This goes over FBIK Solver, Goals, Bone Settings, and etc. in depth with recommended practices. A FBIK solver is necessary for IK Retargeting, so let’s dive in!
https://dev.epicgames.com/community/learning/tutorials/YOjx/unreal-engine-fortnite-full-body-ik-setup-for-retargeting-bipeds