I rigged my character with auto rig pro but a disadvantage of Auto Rig Pro that I've experienced is that the arm moves as an FK rig (As opposed to Rigify with its IK arm rig). I've tried to customize an IK of the arm movement by applying an IK constraint to ARP's hidden bone layers. But I cant manage to do it without messing up with the rig. Can anyone help me?
I guess you already found your answer but maybe other peoples will need this too.
Here is one way to do :
Once you have your rig, go into pose mode and select the rectangle part of the hand. Then on the panel on the upper right of the screen go to "tool"
Under Rig Main Properties you have "IK-FK Switch". 1 = FK ; 0 = IK
So if you want IK, switch it to O. I hope this will help.