Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Source Character
CS_SOURCE_CHARACTERParameter: Target Character
CS_TARGET_CHARACTERParameter: Go to Reference Pose
CS_GOTORESTPOSEParameter: Transfer Mode
CS_SOLVERMODEParameter: Strength
CS_GLOBALSTRENGTH