Question Help!: Questions About IKs and Animation Rigging

Good Day everyone;

Well... since Animation Rig is now available as a preview package, I wanted to study it since It's a feature I've wanted for Unity long time now. About that, I have two questions about it.

1. I've seen many tutorials create a "Runtime Rig" empty where they will add the "Rig" script and the constraints such as IK or Rotation Constraint are created on another empty and made children of the Runtime Rig object. But mostly, models that come from an animation program already have IK and constraints remaints on them, such as IK target objects, Poles, Helper bones that were used in the animations, they may not be functional depending on their previous use but they are still there. for instance, If keep creating Runtime Rigs and more and more empties to become constraints, soon enough my model/prefab will have a lot of junk in it (Unused stuff). My question is, is It possible for me to reuse the preexistant objects and have them once again set up to work for me instead somehow?

2. On the tutorials I've seen, a person adds IK, now he/she controls the arm. But If we take a closer look, the whole body is animating while the arm is standing still at the IK target point waiting for commands. But, If, by example, I have a walking animation, which I want to make it dynamically adapt to the terrain and environment for example, I would want even the IK constrained bodyparts to follow the original animation and only leave their standard path when disturbed by the environment. Or maybe, I have a gun holding stance which I want to use IKs only to adjust where the character is aiming at. How could that be achieved? Or will I have to reanimate the constrained limbs all over again?

Thanks,
Arthur