Depends on the part. Some need it. some do not.
Either way so long as the skeletal mesh isn’t set to simulate physics, even colliding with other mesh parts would not affected it. It depends.
No, you just leave em blank.
Should be grayed out, but also toggled to false.
You shouldn’t be able to directly toggle the switch from any skeletal mesh components you add - consider migrating to a new character blueprint. (easier than figuring out why it’s toggled).
Sounds like your parenting is off.
Have you attached the mesh correctly, and removed their local transforms?
Sounds like master pose component is running, or you wouldn’t get animations at all (t-pose). I run mine on construction, so the blueprint can be used to preview full animations anywhere. Same difference if you have it elsewhere. so long as you do have it.
There really isn’t much else to it:
Main mesh with assigned Phat asset.
Parented parts with no phat asset.
Capsule component set to Pawn (optional toggle Generate overlap events on).
Main mesh (and sub parts) set to CharacterMesh (optional toggle Generate overlap events on).
Master Pose component on begin play or on construction. So long as it’s somewhere.