Honestly I think there’s a tendency for people to really overthink the mocap+retargeting thing.
I did this test recently - I started with a pretty poor mocap file I found of a person doing a forward roll.
My workflow was basically :
1 Retimed the mocap to make the action more dynamic (real life timing is often a little dull… )
2 Scaled up the mocap skeleton roughly to match my character.
3 Posed my character to match first pose of mocap as best as possible and then constrained the main controls of my rig to the skeleton using point/orient constraints (I don’t go nuts here, the main body control, the chest Ik, head maybe and IK arm/leg targets and poles are pretty much it…)
4 Baked the animation to the rig.
5 Deleted the mocap and constraints and then hand-finessed the animation from there (the guy in the mocap suit wasn’t holding a giant axe for example
6 Added extra stuff to the end where he stands up (wasn’t in the mocap file at all).
The results after steps 1-4 weren’t pretty but they were a good starting point for finessing to suit my character. That’s pretty typical in Mocap really, it’s never a 1:1 fit in my experience even if your character has human proportions. Ignore what the marketing people tell you about this, they just want to sell you stuff
I did it in Maya but the same thing should work in C4D once the constraints are working ok. I can’t remember if C4D has a ‘maintain offset’ option when creating rotation constraints but you definitely need that as the orientation of the rig and the mocap skeleton can be very different.